This is of course true. Some of us are not very comfortable with having cameras around, but for a lot of people out there, it's interesting to get a glimpse of the studio work, so it's not a huge sacrifice to have a friend putting together a professional and entertaining series of "webisodes" that will also build up anticipation for the album. If this in turn translates to more album sales and exposure, we'll have better chances to get good touring/festival offers (which is a VERY competitive thing right now), and then it's win-win and definitely worth the embarrasment of appearing all tired and sweaty on YouTube trying to play a guitar part right for the 10th time.
And no, there's no contractual obligation at all, but reality is that in order to keep going at this level (especially given the current state of the music industry), we need to promote the band, and that means doing things that wouldn't necessarly have been done without the marketing aspect. We've said no to a lot of stuff that would have been good exposure but just wasn't right - but most of these small things (signing sessions, interviews, video recordings, the occassional venture into sellout territory) aren't that exhausting, and they're part of the game.