There's been a lot of discussion about the recent New York Times article How Yoga Can Wreck Your Body, published January 5, 2012.
The article is negative and alarmist in nature, citing anecdotal evidence of yoga students and teachers who have badly injured themselves, and stating that many yoga poses are inherently dangerous for most people.
Well, sure, if you take the average person off the street who has no yoga experience and have him do a headstand or a backbend, of course there'll be problems.
Of course people can hurt themselves doing yoga poses, just as people will get hurt doing any kind of physical activity. I've hurt myself practicing yoga poses -- I didn't know there was a problem with how I was doing those particular poses until it was too late (I certainly learned from those injuries!). But there is nothing inherently wrong with doing any of the yoga poses with the right instructions and preparation. Some people will never do many of the more difficult poses, and they shouldn't try, for various reasons. Others can practice these poses after they develop the strength, control, and awareness to bring their body into the alignment necessary to keep them safe. Accidents / injuries can occur, but they can also be reduced.
It depends on how skillful the teacher is, and how capable the student is, mentally and physically.
The good that has come out of this article is that there is this discussion about what it means to practice yoga, and how to practice the asanas in a safe, intelligent manor.
The bad is that some readers will take this article at face value and be afraid to try a yoga class that could be helpful and appropriate for their own bodies, thinking they'll have to do dangerous poses and risk suffering from severe injuries or stroke.
Luckily there have been many well-reasoned responses to this article from skillful, highly-trained yoga teachers and very experienced yoga students from different lineages pointing out errors and misconceptions in this article.
Read the response from Intermediate Junior III Iyengar Yoga teacher Roger Cole on Facebook --
Roger points out that the article seems to imply that B.K.S. Iyengar teaches Salamba Sarvangasana (shoulder stand) in an unsafe way, having people over-stretch their neck which could lead to damaging the vertebral arteries. The NYT article also says that Roger Cole was the innovator of the safer way to do shoulder stand, using a blanket platform under the shoulders so the neck wouldn't over-stretch.
Roger sets the issue straight, correctly stating that B.K.S. Iyengar is the one who developed this blanket platform system, and that Iyengar insists students practice Sarvangasana with this support.
Read Roger Cole's article on YogaJournal.com, Keep the Neck Healthy in Shoulderstand to learn how this way of practicing shoulderstand protects the neck.