Let's get the bad news out of the way first: pre-roll ads are coming to YouTube on Android in a big way. Big G is adding the digital speed bumps to "tens of thousands of YouTube partner videos" starting now, but it's for a sort of good reason: Katy Perry. Well, her and a bunch of other music videos, all appearing in the YouTube 2.0 app on Android, with the initial batch provided by VEVO. Music videos will be identified by a note icon and, while you're watching one, you can get artist info and quickly view other tracks that are available. Right now this is a feature only available on Android but, with Google happily extolling that it drove a 300 percent growth in mobile video viewership in 2010, we're guessing it'll be coming to other platforms soon enough.