The thing that turns me off from yoga (and Tai Chi, and other similar exercises) is how to go about learning it. I feel that if I attempt to do something out of a book or video, I'll end up doing it wrong, which might end up screwing up my posture or something. And classes are either costly, or I have to find a good time to attend them, and I don't know which type of yoga would be the most beneficial to me.
It's not that I don't want to learn, it's just that I don't know how to go about doing it. I figure that it would benefit me more if I start sooner than later.