We've not come across wires on our local rides, but at the end of last year while the nights were still bright and the trails had more and frequent traffic, we started finding more and more trees and branches dragged out and laid across the trails, one of our regular riders had an off on a popular section as we were heading down it, a huge tree trunk had been left in the middle, and covered over somewhat with leaves, he didnt see it till his wheel hit it and spat him over the bars!
Thankfully he was fine, but things like that truly boil my piss, if i ever caught anyone doing it, id bat them over the head with (insert whichever bike name i would be riding at the time here) lol
***Disclaimer, I probably wouldn't indulge in violent activities, the above statement is purely for keyboard heroics!***