I recently read a couple of interesting articles....
Yoga Injuries: The Bigger Picture from The Yoga Journal which was a response to "How Yoga Can Wreck Your Body" article published in the NY times.
I can only speak from my experience. I have yet to acquire a yoga related injury... I practice often & sometimes quite deep but I always listen to my body and my breath. I believe strongly in knowing your students well enough to assess their physical & ego related weaknesses as well as their strengths. One of the hardest tasks as a teacher is insisting a student not continue deeper in a pose or that they should avoid certain poses until ready..... oddly enough, the occasional student will ignore or question your advice. As teachers we are here not only to train the body but owe it to our students to teach them how to check their egos for the sake of their body. One of my favorite quotes being.... 'Never sacrifice the body for the glory of the pose.' At the end of the day: you can lead a horse to water.... but you can't make it drink.
Play safe! I would if I were you :)