In the nineties my pony had a pole down at a competition and I was advised to jump him over barbed wire to teach him to be more careful. Happily for him I was not a stupid child.
I went to a regional final of a showx competition recently, and there was a team relay competition held at each height open to all. A local dealer won two of the classes with the horses he had for sale and they were fast and clean, but they had all been rapped. The double snap on the front end spoke volumes, and some of them were lovely looking and moving horses. Barge pole.
I brought one 10 years ago that I still have that's definitely been rapped. The only time he's ever stopped with me in this time, including if I've got a horrific line to the fence is when 2 girls were standing either side of the fence as they had just put it up for me. He just froze. Girls walked into the middle and he popped straight over it. It's definitely becoming more common, but I hate it, unfortunately I imagine it would be very hard to police if banned (although I'm fairly certain it's frowned upon now). Sorry I've not read any replies, so apologies if this is all irrelevant!
I liveried at a yard, where a couple of the jump poles belonging to one of those awful competitive mums had crown bottle tops nailed to them. The ponies were always ridden in a gadget of some kind or other and were some of the saddest, most jaded looking things going. Thankfully, they were kicked off the yard. Horrible people and were they successful? Nope.
Spiked boots appear to be quite popular with some too. Vile practices.