My small site probably gets 15 bogus sign-up attempts a day and even more attempted SPAM posts. But in the month I tried CleanTalk, there was not a single bogus registration or successful SPAM post. I've now signed up for the paid subscription!
Better yet, if you're designing a web site, CleanTalk is totally passive and eliminates the need to configure Captcha for log-in screens, registrations, and forums etc.
It just simply works!