Recently, the Occupy St. Louis Facebook Group passed the 6,000 "likes" mark on facebook, after only being in existence for a month. This puts them well ahead of the St. Louis Tea Party, which has been in existence for several years.
It's also worth noting that unlike the Tea Party, the Occupy facebook group grew by true grassroots support. The tea party facebook group's growth was based on a big facebook ad buy, so broadly targeted that even I (an unlikely target) saw ads for several months. On the other hand, the Occupy group grew by word of mouth and sharing.
So it's nice to know that when it comes to astroturf vs grassroots, money can buy you some people, but it can't quite buy enough people to outpace an actual grassroots movement.