Adobe announced yesterday that they will be adding H.264 video playback to their Flash product. I have to 
wonder whether or not YouTube knew about this move. YouTube uses .flv videos as a standard on all of their videos however ever since the AppleTV was capable of playing YouTube videos YouTube has also had H.264 versions of some of their videos. YouTube had also said that they were planning on transcoding all of their video to H.264 sometime this fall. Many have thought that this was just a way for the iPhone and AppleTV to have access to all of the videos or maybe to save on disk space.
YouTube may have done this knowing that Adobe was going to add this support. YouTube may have decided that since .flv videos are so much larger then H.264 that moving their entire library to H.264 would save a ton of money in bandwidth costs.
Adobe’s press release also states very clearly that they will support HD resolution as well making me also wonder whether or not YouTube will shortly go HD.