I think it really helps to set up two or three signup questions that require some thought to answer, and that require an answer. My site, among other questions: "My interest in mountain dulcimers, or where I first saw or heard one"...and also "What sweet edible substance do bees make?"
I do have my site set to Admin Approval as well, and anyone suspicious I will look up the location of their IP address. Spammers get their IP address banned with the Jamroom Ban module...I ban the whole range of the ip address- just leave out the last dot and the numbers after it when putting the ip in your banned list. That will also ban when they reset their ip.
With this system, I have not had a single spammer or bot even attempt to join up in my first four months live. They don't want to even bother answering questions about music or nature...lol.
...just another satisfied Jamroom customer.
Migrated from Ning to Jamroom June 2015
updated by @strumelia: 26 Oct 2015 08:00:23PM