Try watching a music video on the iPad. Even the ones on Youtube don't work. (They don't even come up in searches from the iPad app.)

For instance, this seems like a normal YouTube link, except it doesn't work on the iPad: http://www.youtube.com/watch?v=GQ95z6ywcBY

Edit: Wow, I hadn't realized how bad it was. YouTube is also blocking all the fan-made videos from the iPad. For instance, this one is a Lady Gaga song with lyrics overlaid: http://www.youtube.com/watch?v=CAoi_-_EVio