Interesting thread. I've been biking for over 20 years now and have only worn a skirt on a bike once, while on vacation in Florida... I rented a beachcruiser and was wearing a knee length, wide A-line skirt. There was enough fabric that I could sit on it in such a way as to not worry about the wind kicking it up.

For commuting, I generally want to ride fast (at least on the way to work). Any kind of worrying about Marilyn Monroe skirt moments, clips to hold things, wardrobe malfunctions, etc. would be distracting and slow me down. I ride in bike clothes: shorts, tights, jersey, etc. and change clothes at work. I do, however, keep a bunch of skirts at work. I find that I cool down easier and feel more comfortable wearing a skirt after the bike ride while I am at work. I try to keep all my office clothes synthetic as well, mostly polyester skirts/tops.