I just discovered something. I use my iPad and when you post a video using the YouTube button on the new message screen, I get a "you don't have flash, nananana" message and it can be a chore to extract the weird number of the video, find YouTube, plug the weird number into the search bar. Then half the time there's an error telling you that there is no such video.
But. If you "copy link" from the little arrowy thing in YouTube and paste THE WHOLE LINK as a link in the message dialog box, the video shows up RIGHT IN THE THREAD!
Wow. Try it, you'll like it. And it's so much easier.
And I'll love you for it.