I've witnessed a few people try to step over them without realising they were live one even touched the fence on the off pulse and then cocked his leg over. I am always torn between warning the person or having a blo0dy good laugh at someone else's expense. So far "Good laugh" has come out on top.
Quite a few years ago I worked as a Auto Technician and one of the guys in the garage where I worked removed the electrical part of a spark plug testing machine, which he would occasionally connect to customers cars with a crocodile clip just before they came to pick them up. After paying their bill they would try to open the door and get zapped. Invariably they would go back into the reception to complain and the receptionist who by now was heartily sick of continually having to explain, he told them that the shock was caused by man made fibres in the tyres building up static. Sometimes the receptionist would have to go out and touch the car himself to prove that it was ok now. It was cruel I know but funny at the time, its a wonder they never actually killed some poor sucker.