I'm a big fan of StackOverflow on which I am a frequent contributor. If you are a programmer who is tired of trawling forums filled with old answers or using the "evil hyphen site" (as Joel puts it) then you should seriously go check it out. Joel Spolsky (of Joel on Software fame) recently gave a Google Tech Talk about StackOverflow that is well worth watching.
StackOverflow does a pretty good job of keeping spammers and abuse away while remaining open and accessible, although in February they were forced to limit question and answer rate for new users in response to one particular incident.
Joel correctly makes the point that behaviour is to some degree a function of environment. And herein lies my particular beef. Jeff Atwood (of Coding Horror fame), when discussing the StackOverflow Question Lifecycle said that:
...take a long, hard look at how bad the sofaq tag has become...I spent a few hours cleaning it up tonight and I barely made a dent in the sprawling mess it has become.
Just today I decided to do a little clean up of my own and remove the "gae" tag. It was used 15 times. Out of those 15 questions, 14 were also tagged "google-app-engine", which is used over 200 times already. So basically it is superfluous. Anyway, in the course of retagging a mere 15 messages I was presented with CAPTCHA SEVEN times!
Now I'm all for keeping spam and abuse at bay but this has reached the point of discouraging positive behaviour ie cleaning up the site. So it should come as no shock that messes like the SO FAQ have come about and will no doubt persist.
Interestingly, I recently came across an article titled The Death of CAPTCHA. Personally I look forward to the day that we have some better solution than challenging legitimate users with sometimes almost indecipherable sigils (have you seen Google's own CAPTCHA?) that really turn a lot of people off.
At some point you just have to look at the content or what's being done and not just use brute force rate limiters as a band aid solution.