Messy weather is when brakeless seems to work best for me. I always run a brake because usually my gear (47/16) is too high to comfortably skid or skip, it's hard on my knees (which are already suffering from years of inline street skating abuse--note that this is in direct contradiction to the first reason), and brake pads are cheaper than tires.

BUT when it gets nasty out, I run a lower gear on my other bike and I'm generally more cautious. That pretty much takes care of all of the above excuses and I don't touch the brake nearly as much if at all. Just my $0.02.