While I nod to my colleague Colum Lynch's sage article on the dangers of using Twitter as a reporting tool, it's notable to see a great deal of activity on the Chinese Twittersphere -- even at 3 a.m. -- forwarding news of Mubarak stepping down. You can follow yourself here.

A few sample tweets, roughly translated:

"I am very optimistic about the future of Egypt. There are new national heros and they have acheived such an important victory, no matter what the future difficulties."

"In China, the next change will not produce another Tiananmen Square. People are learning. A lot of people are surprised at the sophistication of the Egyptian opposition groups' strategy, and also at the Egyptian military's power of restraint."

"An Egyptian blogger wrote: 'This is no leader of the Revolution' and 'three million individuals have chosen hope over fear.'"

UPDATE: China's Foreign Ministry hasn't yet released a statement in the wee hours, but I expect official reaction will be similar to what Chinese Foreign Ministry spokesman Ma Zhaoxu told a press briefing yesterday in Beijing: "China holds that Egypt's affairs should be decided independently by the country without foreign interference ... We believe Egypt has the wisdom and capacity to find proper solutions and get through the current tough time."

Just seconds after Hosni Mubarak resigned, African commentators started tweeting. "After #egypt Is the rest of #africa listening and watching? Support the protestors in #gabon #sudan #libya #algeria #cameroon #uganda ...." wrote Emeka Okafor, author of the Timbuktu Chronicles blog. Ferial Haffajee, editor of South Africa's City Press newspaper remembered the last time she'd seen something so moving: When Nelson Mandela walked out of prison exactly 21 years ago today. Then, she promptly asked, "So, if Mubarak's gone, why not Gbagbo and Mugabe too?"

Egypt is an African country, too. And while the protests have rocked the Arab world, unsettling autocrats from Algiers to Riyadh, it has equally shaken the ground under Africa's strongmen. Other tweeters report that Zimbabwe's Robert Mugabe is censoring the news of Egypt's protests. In Gabon, protesters took to the streets bearing banners that read, "In Tunisia, Ben Ali is gone. In Gabon, we've still got Ali Ben," (Ali Ben being a reference to president Ali Bongo Ondimba, son of the former strongman Ali Bongo). As protests broke out in Algiers today, the headlines read, "Waiting for the revolution in Algeria."

Across the continent, Mubarak's fall isn't being read as the end of the Middle Eastern autocrats. It's being read as the end of autocrats. Period. The people power that ousted Mubarak today has not been witnessed on the streets of Nairobi or Lagos or Kinshasa since the end of colonialism. Yet many of the presidents in power are the same men (or their sons) who took power back then. 

Like Egyptians, the Congolese, Nigerians, Eritreans, Senegalese, Angolans … they know what their regimes are like. They mock them, curse them, and sometimes fear them. But with each day of the Egyptian protests, there was a growing sense that they can also defeat them. As one Zimbabwean tweeter wrote today, "Next time you hear a dictator say he is not going, know that if you push hard enough they will go. #Zimbabwe #Egypt."

There's been a fair amount of speculation in recent days about now ex-President Mubarak's preperations for departure. I just spoke with Christopher Davidson, a professor of Middle East studies at Britain's Durham University who focuses on the economic interests of Arab rulers. He cast doubt on the $70 billion figure which has been floated widely by the media recently, but said Mubarak undoubtedly has interests throughout the world to fall back on: 

There would be something wrong with the people he paid if we knew much about this. A lot of the figures we've seen in the press are really just speculation. As with Gulf ruling family, his wealth is hidden abroad very carefully with layer upon layer of shell companies in London and the States. There's also a big question about his numbered bank accounts in Europe, whether he will be able to recover those or not.

Davidson speculated that Mubarak's ability to recover funds from his Swiss bank accounts, and the difficulties his now partner-in-exile Jean-Claude "Baby Doc" Duvalier has had in recovering his own assets, may have played a role in his delayed departure:

I would imagine that he'll struggle to recover everything. A few weeks ago we had the Baby Doc ruling in Switzerland, so that will clearly be playing on his mind. I suspect that this is one of the reasons why he was trying to hold on as long as possible, so he could portray himself as having resigned peacefully as a legitimate president rather than having been ousted.

Despite having now holed up at his "Winter Residence" in Egypt -- which is less a palace than a floor of a luxury hotel and golf resort -- and his earlier promise to die on Egyptian soil, Davidson believes that Mubarak is not long for Egypt:

He'll be headed to the Gulf for sure. Perhaps not to Saudi like Ben Ali, but I think he'll go to the UAE. [UAE Foreign Minister] Sheikh Abdullah bin Zayed visited Cairo quite publicly and likely put a plan on the table to give him refuge.

Update: Sure enough, we now have reports that Switzerland is freezing Mubarak's assets.

It's official:

A massive crowd in Cairo's central Tahrir Square exploded into joy, waving Egyptian flags, and car horns and celebratory shots in the air were heard around the city of 18 million in joy after Vice President Omar Suleiman made the announcement on national TV just after nightfall.

"In these grave circumstances that the country is passing through, President Hosni Mubarak has decided to leave his position as president of the republic," a grim-looking Suleiman said. "He has mandated the Armed Forces Supreme Council to run the state. God is our protector and succor."

More to come.

Writing on another anti-authoritarian revolution which took place three decades ago, historian Timothy Garton Ash described the fundamental philosophy of activism espoused by Polish writer and opposition leader Adam Michnik: "Behave here and now as if you lived in a free country." It was only by moderating your behavior to fit the political reality of dictatorship, Michnik and his Solidarity cohorts believed, that you legitimated its authority. 

In a perverse twist on this idea, the statements coming out of the Egyptian regime in the past few hours seem predicated on the notion that Egypt is a democratic country bound by the rule of law. 

In his speech, Mubarak referred to his "responsibility to protect the Constitution and the rights of people until power is transferred to whomever the people choose during September, the upcoming September, and free and impartial elections that will be safeguarded by the freedom -- the call for freedom." He also guaranteed the "supervision of the upcoming elections to make sure it will be conducted in a free manner" -- as if his regime had had nothing to do with the fact that previous elections had not been conducted in such a manner. 

He went into specific detail on proposed amendments to the Egyptian Constitution, as if the country hasn't operated for three decades under an emergency law that allows that constitution to be suspended in the name of national security. 

Speaking on CNN just now, Egypt's ambassador to the United States, Sameh Shoukry, argued bizarrely that "President Mubarak has transferred the powers of the presidency to his vice president, who will now undertake all authority as president," despite the fact that Mubarak seems to have no intention of leaving office.

Again, the idea of Mubarak remaining president in name only while all authority is transferred to Suleiman makes some sense if you buy the notion that governing authority in Egypt is constitutionally proscribed and that Suleiman is an independent political actor rather than a loyal confidant of the president since their army service. As long as Mubarak is in the government, who has the "authority as president" is a technicality. (Somewhere, Dmitry Medvedev is chuckling right now.)

Unlike the system Michnik sought to overthrow, it is now the regime that is pretending it operates in a free country, using the democratic trappings of elections and constitutional amendments. Judging for the reaction in Tahrir Square tonight, the people of Egypt don't seem to be buying the idea.  

Egyptian opposition leader Mohamed ElBaradei, who spoke with our own Blake Hounshell earlier today, seems to be calling for the military to oust President Mubarak in his two most recent Twitter messages. 

In English he writes:  Egypt will explode. Army must save the country now

Another message in Arabic (Google-translated) is even more blunt:  I demand an immediate military intervention to save Egypt. The credibility of the army to the test

It's hard to see why Hosni Mubarak is so reticent to leave office -- not least because he woouldn't exactly be retiring to a life of austerity. According to a report first published in Al Khabar, the family fortune that would await the departing president could amount to as much as $70 billion.

How on earth did the Egyptian president get so rich? (For some perspective: Egypt's GDP is only slightly more than twice that amount, $188 billion.) The answer is a combination of corruption and business deals forged with foreign investors and businessmen in Egypt. Mubarak also owns countless homes and several hotels, which contribute to his family's assets. 

At least some of this wealth is reported to be held in offshore accounts, notably in Switzerland. But here's some bad news for Mubarak: On Feb. 1, the Swiss government passed an interesting piece of legislation that will make it much easier for countries to repatriate illictly-stolen wealth from past dictators. One of the first applications was the wealth of Haitian ex-strongman Jean-Claude Duvalier, which has now been frozen and may well return to the government in Port au Prince.

Of course, Mubarak has lots to answer to and economics are just a piece of it. (For a extensive catalogue of all the reasons not to feel sorry for his beleaguered regime, check out our FP list.) But time and time again, illict wealth has been the achilles heel of ex-autocrats who might otherwise live their lives in quiet exile. Chile's dictator, Gen. Augusto Pinochet, for example, still had great public support until his people learned how many billions he'd stashed away. Countless other autocrats (including Tunisia's ousted President  Zine al Abidine Ben Ali) have met a similar fate.

So much for a quiet retirement in Sharm el-Sheikh.

Update: There is some disagreement about the size of Mubarak's 'estate' -- another estimate reported by MSNBC's Open Channel blog puts the sum at a still-healthy $2 billion. Lawyers and activists will be nailing down the exact sum, undoubtedly, for years.