Had a bizarrre incident here the other day. Although we ban climbing with mobiles, this guy must have sneaked it up the climb with him while toproping, clipped to his harness I think. When he got down, there was his phone, clipped to the rope on the belayer's side of the top pulley about a metre from the top, just hanging there. The only explanation was that when lowering off, about half way down he brushed the other half of the rope & the phone got caught on it.
I can't remember any serious head injuries in 11 yrs I've been at the gym, don't think they should be mandated. The draft Australian Standard (should be out next year) says:
"A risk assessment shall be conducted to determine if there is a particular hazard for which head protection is required. Helmets are not generally used on fixed ACW. Helmets, if used, should be chosen based on the type of protection being sought."
That last sentence was due to debate about whether the helmet is needed for falling objects or for heads colliding with walls, the floor etc.