Twitter is down. Facebook is experiencing intermittent problems. The world is going to end. Currently, Twitter is defending its servers against an DDoS attack. More about denial of service attacks here.
Twitter has shown its importance during the Iran election debacle a few weeks ago. It was the main way for citizens to get news out about what was happening inside the country, as the government wouldn’t let much out since it has a firm grasp on the media.
It’s a quicker, ephemeral medium. Much more so than blogs, and those are also ephemeral and quick compared to traditional media. It’s launching the real time web, which is something very exciting.
Update: It appears that the source is a Georgian blogger’s account. Twitter, Facebook, Livejournal and Google’s Blogger were targeted. While Google was never affected, and Facebook worked well but with intermittent problems during the day, Twitter is still out of commission.