I used always have to remember to include a direct link to a YouTube video whenever I embedded one on my site, so iPhone users would be able to tap it and be directed to the YouTube player. Fortunately, now that the new iPhone software is being released around the world, I no longer have to do this. Safari identifies the YouTube embeds, and a single tap on the video opens it in the YouTube app:
Embedded videos in Safari.
Tapping on the video opens it in the YouTube application.