I'm not in the skydiving industry so can't comment directly, however I can say that while flying in NZ, I have twice had skydivers appear directly in front of me, jumping through what was in both cases about 7/8 cloud cover; once had a skydiver land in front of me as I was taxying a long distance from the PDZ; another time, listened in to a group of skydivers who were using a local hangar, as they discussed ways to unsettle the aircraft and scare the pilot. I crap you not.
I'm sure the majority are professional, but there are still plenty of the other kind around.
Reminds me a lot of the jetboating industry... all stretching the boundaries until someone gets hurt, then everyone behaves for six months, then back to normal ops.