Exactly. Blocking payments.
Honestly, I don't see much benefit to legalizing on-line gambling, at least not to small-time gamblers. I'm not worried about being screwed out of my measily account. My winnings (however small) aren't taxed and neither is my gambling site which might be why they offer the lowest juice. The current "illegal system" works fine for me.
Admittedly I might feel different if I had $100,000+ in my account.