I worked on my Stop Spammer Registrations plugin this week. It is getting quite complicated. It checks for IP and Username in addition to the Email. I cache recent attempts in order to keep the bad guys out without having to hit the StopForumSpam db more than I have to.
I had to make it backward compatible so that existing users would not lose their record of hits.
I fixed a bug where email was blank, but the ip address failed.
I added the uninstall cleanup. I forgot to add this to the first 3 versions.
As usual, I had to fix up lots of spelling and grammar mistakes in the docs.