I have platforms like those above on my BMX, and I also have the gash in my shin to prove it. To the bone baby. Slipped a pedal and it freewheeled back around to my shin... ouch.

I once forgot my shoes when going to a ride with a friend. Ended up doing 25miles in flip flops... but that was on the roadie. Still hurt the arches of my feet by the time I was done. No way I'd flip flop fixed platforms anywhere further than my driveway (although trackstanding like that was the FIRST thing I did when I put it together )