In addition to Netflix, Flixster, official Twitter and all those other apps demoed today by Microsoft, they also finally gave us a look at their official YouTube app, which will presumably be an optional download in the Marketplace.
While you can't stream YouTube videos directly in Mobile Internet Explorer (not yet at least), when presented with a YouTube link a separate program launches and streams the video. So, familiar territory for Windows Mobile users. No mention of HD streaming though, which is offered on such high-end devices as the Android HTC EVO.
One of the nicest aspects is how the video history is stored under the Pictures/Media hub automatically, allowing quick access (and pinning to a Start Tile) to your videos. That should be great if you're that guy who likes to constantly show off the latest viral videos to your friends...are you that guy? Stop it.
Anyways, between Xbox LIVE, Netflx, YouTube, Zune (music + videos), Twitter, Facebook, etc., Windows Phone 7 finally looks to have nailed down all the corners of social/media tent of 2010.