Bonus abuse comes around a lot where I am focussing on with some websites at the moment; no deposit free spins. What the players do is they make multiple accounts to claim the free spins, just as long untill they make a profit. They then make the necesary deposit and cash out, never to be heard from again in that casino; they will go on to the next.
Thing is, they never make big profits, and some casino’s dont even let them cash out, because they have made multiple accounts. But sometimes they use VPN and use a different ip every time, then the casino can not do so much against this kind of abuse. In the long run though, its just a small fraction of the players that abuse.