Intressant, det verkar som om YouTube kommer att komprimera om sina filmer för AppleTV, så det blir H.264 istället för flash-filmer (FLV):
According to Moody, not all of the Youtube catalog will be available on day one. Instead, "thousands of videos designed for Apple TV" will be available at launch, but that the remainder will become available by the fall. The reason for the delay is that Youtube will be encoding all of their videos into a "H.264 streaming-efficient compression format" specifically for the Apple TV. All of Youtube's videos are currently encoded in Flash Video (FLV) format.
While no official reason is given for the mass shift in encoding formats for Youtube's entire catalog, Macformat.co.uk believes it has to do with the iPhone.