Yesterday on a group ride, just as we were stopping for a brief water/feed break at the turnaround of a 50 miler a wasp or yellow jacket got INSIDE my glasses. I was practically stopped so I quickly pulled the glasses off, closing my eyes as I did so. Unfortunately, the cyclist who had been several feet in front of me had slowed much faster than I, and when I opened my eyes (only closed for a split second) I was right on his wheel, touched it and went down. Luckily I couldn't have been going more than 2-3 mph at the time so it was a very gentle, slow motion, near stop flop over. HOWEVER, my head did bop the concrete pretty vigorously, not enough to damage the helmet, but definitely enough to have caused extreme discomfort and quite possibly injury.
WEAR THOSE HELMETS!