RealTime appears as a toolbar at the bottom of every YouTube page with three main items. The most prominent button is an indicator showing when you have Realtime sharing turned on, obviously to ensure that you don’t accidentally share some videos you aren’t too proud of watching. The ‘Online Friends’ tab shows which videos your friends are currently watching (if any) and their recent history. It also allows you to send an invitation to come watch the video you’re watching, which will pop up on their screen (you can turn notifications off). This is where the real power of the new product lies, as it allows friends to instantly share videos with each other.

Finally, there’s a button for ‘Watching Now’, which allows you to see any random YouTube users who happen to be watching the same video as you. This isn’t a privacy issue because you’re only shown in the list if you opt-in, but it seems pretty pointless. A chat feature with other users could potentially be entertaining (though I’d hope for some decent filtering given the YouTube comments I’ve seen), but what’s the point of a list of people I don’t know?

Aside from that that, I have a few more gripes with the toolbar. Unlike the toolbar on Facebook and some other services, the YouTube toolbar disappears and reappears every time you load a page. This is hardly a game-breaker, but it’s still sort of annoying. I also think that there should be an option to have all of the videos your friends are watching pop up as notifications – in the current version, they have to invite you in order for a notification to appear. But the product is still an early Beta, so there’s still plenty of time for these issues to get squared away.

Source : http://www.techcrunch.com/2009/04/22/first-look-we-take-youtube-realtime-for-a-spin/