[Marianna]

I love Bikrams Yoga - I haven't done it for a few months, but this month I am definitely getting back.
The heat and humidity definitely helps with stretching. You must drink a lot of water before, during and after. I bring a 1.5 liter bottle of water that I previously freeze. During class it thaws out and I have cold water for most of the 90 minute session.
I don't know about others,but the studio I go to do not make you do anything you can't. They emphasize to stretch as far as YOU can TODAY. It is not a competition with others, and not even with yourself. They always say to just lay down on your back if you don't feel right - you don't have to push yourself over the limit.

I think dehydration or feeling dizzy/lightheaded during session is more of a possibility than injury. However both can be avoided easily (in my opinion) don't eat anything for 2-3 hours before, but drink plenty of water/gatorade etc before/during/after. Listen to your body, and don't push yourself too hard.

I'm pretty flexible, but I reached new heights in my flexibility even after 2-3 sessions. So I'm definitely going back, luckily there's a studio 2 streets down from my house.

And no, I don't think it's a fad, I agree with Athallia, something lasting 30 years or so does not qualify as a fad. (cabage soup diet, yes, but not Bikram's yoga/hot yoga)