Pluggable CAPTCHA

CAPTCHA should be pluggable in JIRA CAPTCHA|http://en.wikipedia.org/wiki/CAPTCHA is supposed to stop spam and other automated nefarious usage of systems. But there is an arms race of CAPTCHA breaking|http://www.slightlyshadyseo.com/index.php/xmcps-how-tobasic-captcha-cracking-techniques-part-1/ a...