A lot of runners and triathletes incorporate yoga into their training as a way to stay flexible and reverse some of the muscle and tendon tightening that running and cycling promote (especially if you are bad about post-run stretching). Pilates, which incorporates a lot of yoga into a mat session, is a different animal.
Yoga is not a competition, and yet I think we've all been in a class where someone treats it that way. And it's these Type A's that I'm pretty sure are among the injured. As an instructor says in the article, "It’s ego. ...The whole point of yoga is to get rid of ego.”
Article: How Yoga Can Wreck Your Body