YouTube has debuted a new ability - codenamed Active Sharing that is currently a part of TestTube. Active Sharing was built with a single purpose: that of allowing other members of the page to see who is watching a certain clip.
To start off you can share what you find immediately by Active Sharing with other YouTube users. Click the "Start Active Sharing" button, then go watch some videos. Your username will show up on the page of the videos as you watch them, and a list of the latest ones you've seen will appear in your profile.
Your username will appear on a certain clip's page if you enable the feature from the TestTube page, but it is displayed only for 30 minutes. A list of the clips you've viewed is also created on your profile page, helping you to organize the videos easier than before.
I have no idea if this update was designed to make YouTube more competitive for the other similar services on the Internet but it brings an impressive new functionality to the users. Recently, YouTube was threatened from all around, no matter if it was a company that sued Google for copyright infringement or a rival that prepares a new solution. On Friday, Google's online video sharing service recorded the first major hit after Sony debuted eyeVio, a similar service that is currently available only for the Japanese users.