From an article on ThinkProgress.org:

Over the weekend, thousands gathered for a “Tahrir Square”-style protest of Wall Street’s domination of American politics. The protesters, organized online and by organizations like Adbusters, have called their effort “Occupy Wall Street” and have set up the website: www.OccupyWallSt.org. However, several YouTube users posted videos of themselves trying to email a message inviting their friends to visit the Occupy Wall St campaign website, only to be blocked repeatedly by Yahoo.