I had been bombarded with registration spam from a couple different bots. I attempted to track the few IP addresses that were used. I was sent all over the world. I knew I couldn't track them down and stop them so I looked into SPAM prevention plug-ins. I have ReCaptcha installed for all forms and registration. And I am using Mingle for a forum plug-in and the bots used Mingle registration as well. The first plug-in I used would look at new users and auto delete the users if they had not posted in a set time. That was not really what I needed. I had around 20 new registrations within 30 minutes if I turned on sign up. I set up this plug-in and acquired API keys for the different services. Once setup and running, I have not had any SPAM registrations at all over the past 5 days. Amazing plug-in! I am using WordPress 3.2.1 with Mingle forums.