Anti-Splog recaptcha at user registration?

I’ve had the Anti-Splog plugin installed and set up for a couple of months now. I decided to test user registration just now. There was no reCaptcha function. I checked the settings and it looks like its set up for it – keys are there and reCaptcha is selected. Is this just for registering new blogs, or is it supposed to perform on user registration? If so, where should I troubleshoot? If not, do I need user registration reCaptcha? If so, what is a good plugin for mu/ multi-site?