In the forum that I previously mentioned only a few of us have spam removal authority. And we are responsible. The key is that we are spread across time zones. It is a little tricky when there are replies to spam or grossly abusive posts because simply deleting bad posts from one user leaves holes in the dialog.

In another forum it was clear that certain IP address ranges were "risky". These were blocked. Blocking ranges is not necessarily effective because the spammer could operate through a bot network.

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At one point I was the webmaster for a youth sports site. It amazed me that the spammers had quality control. The spammers were attempting to use an old forms exploit to send pedophile junk to the site admins. Our forms were not exploitable, but I could see the attempts. I started playing with the spammers by changing the address of the forms, causing their attempt to obviously fail. They did not respond to my first change for a few weeks, then they updated. I immediately changed again, deliberately changing the file names in a sequence (file1, file2, etc.) The next response was only a couple weeks later, then a week, finally an hour or two. At that point I figured that I had their attention and an IP address very close to the source, but I was bored and we were not using the forms any more so I deleted them. Maybe the spammer is still trying to guess the address.