I reported two players I thought were chip dumping on poker stars
. It didn't affect me, I won the double or nothing tourney it was in. Poker stars sent me an email stating they found proof that they were colluding and reimbursed players that were affected after closing their accounts and taking their money to pay back the players they cheated.
It is always a good idea if you suspect cheating to report it. I don't mean if you get a bad beat, that happens. Poker stars stated that since I won I woudn't be getting any money. I knew this in advance, I was looking at all of the other players they were cheating. It was a 5.00 buy in, not too expensive but expensive enough. I kept their names and noticed they were in more tourneys together.