While Biz names no geopolitical forces I immediately assumed the culprits were supporters of the Iran Election thieves, but FT.com points the finger at a veteran cyberbully--Russia, who apparently has gone after Twitter, Live Journal and Facebook in order to silence an Georgian citizen who charges Russia with all sorts of nastiness in his country.
Russia, was the first country alleged to launch a cyber attack. Back in September 2007, it went after Estonia when the former satellite country relocated a statue salutary to former occupying Soviet soldiers.
In this case a country has maliciously attacked a few Western social media companies who allow people to speak up. Russia seems to think it's justifiable to silence anything that allows voices it doesn't like to be heard.
This is really scary.