I know many services block or negatively rate connections coming from hosting providers. Personally we see that most of the spam attempts are via cheap VPSs. I'm not sure if they actually hack these or simply just purchase a $9/month host, install VPN, and go to work on spam. Our system keeps track of all netblocks and the companies they belong to and we classify those so our site can take action accordingly. Normally we just alert mods if a new user is created or a new first post is placed by a user originating from one of these hosting companies so it can be checked. Banning access totally from these would leviate some work. My personal experience has been that access to my site via VPN services or ips belonging to hosting providers, are mostly spammers. I think that eventually everything will go anonymous and that will make it much harder to detect and filter spam/fraud. It's going to take smarter tools and changes on sites to detect spam/fraud by usage patterns instead of source. The sad part is that these changes will effect all legit users negatively in order to try to prevent the few bad apples.