Captcha is a good idea. There are system available for blind user to lets talk the captcha letters. I see this on an other forum system. There is a button to submit the captcha code with sound output. This resolve the problem.
If you setup Captcha you must be take care. Several system already 'cracked' and can be read by special bots. If you like read this:
http://sam.zoy.org/pwntcha/I dont like Q/A lists. This have to be setup for different languages and made it more complex for the admin.
