I finally figured out today why most people don't wear flip-flops while mountain biking. It has mostly to do, I think, with the fact that if you crash you run the risk of getting your feet cut up or mashed or whatever. Luckily (I suppose) I went the simple route and just removed some skin from the top of my foot. I was commuting home from my office on campus, and (as usual) was practicing wheelies and manuals and such, when I had to avoid a kid (freshman?)....
My front wheel slid out (once I had put it back on the ground... I know, 100% my fault) and so I found I was sliding along the ground in a kneeling position with my shin kind of tucked underneath me. At the end of the slide (My jeans left a 4 foot blue skid-mark on the concrete) I popped back up and hadn't even lost a flop... both were still in place, but I had managed to put holes in my last intact pair of jeans. I also put a few holes in myself but nothing worth complaining about. Darn kids ;p
(the lower right scab above my knee is from last week... the new ones are from today)