I have seen that, I have done that, and I still maintain that pedaling backward on a fixie is nothing like a coaster brake. Try it at 25+ mph without slowing your cadence. You CAN get hurt. It is possible to stop that way, but it is dangerous, difficult and not as quick or reliable as brakes of any kind.
Come up on an intersection at a fast clip, try to stop that way and see how well it works. Yes, it's all about skill, technique and experience, but most people thinking they want to get into the fixed crowd don't possess those traits. More likely, they will be severely injured should they try. But hey, who am I to tell them not to thin out the gene pool?
Speaking of crazy stuff done on fixed bikes, look up a video called Macaframa. THAT is crazy.