I was having problems with surveys getting spammed because I didn't want everyone taking the survey to have to register for my site.  I have since found a forms component that uses this captcha plugin and there seems to be a friendly amount of resources offered for those looking to write plugins for systems like Joomla.

Here's the link:
http://recaptcha.net/resources.html

It works extremely well on the other forms and is very user friendly.  I would be able to offer the surveys on several other sites if this was included.  Right now clients don't want it because spam fills up the results.

I'm trying to be proactive.