I've been in situations where sights have prevented me from being able to shoot, like in low light, or when I needed to cant the bow to clear obstructions. I've had pins vibrate loose and move. I've broken fiber optics. I've bent sight bars when I've accidently dropped my bow. At one tournament, sneaky #%*! took a pair of pliers and bent my 30 yard pin while I was getting a hotdog and drink!

I don't have problems with sights any more though. I don't USE them any more.