O.K. So, thanks for all of the helpful, pertinant information about this particular batch of spammers.
* Looking through the thread, a horrid realization dawns on self *
OMFG, I've become what I hate the most! I've become a spammer!
* Runs off to cry in a corner *
:p
in the last week i have had 400+ spam account registrations.... D:
Bearing in mind that doubles my userbase!
In the past 2 weeks, despite spamming my site almost everywhere I visit, I've had maybe 3 spammers register. One hasn't posted yet so I don't know if they actually are, another was obviously not really a spammer, and the last volunteered himself into the spammer group. This is despite having next to no restrictions on registration (you don't even need a valid email address).
Maybe you should start advertising that you're tracking the spammers. Works plenty well for me.
You may be onto something.