My current acceptance rate on istock (for recent images) is excellent, and most rejections are for similars. I'm shooting still-life type shots, different subjects under very similar lighting (strobes and reflectors) and it works well. However, I don't even bother taking my camera outside anymore. Too many rejections for lighting from outdoor shots.

Wow
Averil catch on strobes
Only on iStock they dont say to you that they will earn you pay back
Sorry Averil I cant help myself with stupid argue

Yeah, I don't think there are any big conspiracies there, so you may want to put down the tin foil hats. I probably have a better approval rating than a lot of exclusives, but I still get rejections. I think they have a good reviewal process, but (like most agencies) it depends on the reviewer's interpretation of the rules.

Personally, I've come to realize that I'm not always going to see eye to eye with every agency's acceptance policies, but I still think most of them are reasonable. I hope it stays that way, but I'm sure I just jinxed myself.