Ustream has just started to roll out a new feature for its live video streams that allows commenters to syndicate their thoughts across four of the web’s largest social sites: Facebook, Twitter, MySpace, and AIM instant messenger. The feature will go live for Featured shows beginning on Monday, and everyone else will have access soon thereafter.

The feature is similar to what Facebook has offered for its video broadcasts (like the one it had for President Obama’s inauguration), where users are invited to update their statuses in real-time as they watch a video. Except with Ustream’s comments, users will be able to check off boxes at the top of the chat window to choose if they’d like to broadcast their updates across multiple services. Each update from the Ustream ‘Social Stream’ box will also include a link to the video you’re watching, which means that the feature can help videos go viral quickly.