I've read of VPNs that are located offshore. Are those IP addresses registered as well? I recall helping attach an add-on to other forum software (vBulletin) to block trolls. It was a central database where any forum admin could continuously add IP addresses and email addresses to it. You attach the API to the forum so those addresses were prevented from creating accounts. Of course, there are always holes. You sometimes block valid folks whose ISPs assign dynamic IP addresses, and the new guy happens to get assigned an IP address that got blocked because it was previously assigned to a troll (I think AOL used to be a big issue with this back in the day.) It was interesting how often you ran into that, as though the number of IP Addresses was not all that large. I know that every time I restart my Verizon MyFi receiver, a new IP address gets assigned.
@John Brunner, that sounds like the forum spam registry we use here. I don't actually block the ones that are matched as forum spammers but they are flagged and if anything else looks hokey on the registration data, I deny them. I can also see how many forum admins had reported them. If only one or two Admin has reported them, it could simply be some Admin who is angry with someone for reasons having nothing to do with actual spam. Otherwise, I just try to remember to watch them a little more closely and sometimes alert Yvonne that they may turn out to be a spammer.
It's silly. I helped on a gun owners forum. That place was a magnet. I don't see much of it here, which sort of surprises me, given the advertised demographic.