Chris,
Captcha is not something that JFBConnect implements. We support it and will check the captcha, but if bots are bypassing it, it's not a problem in JFBConnect, it simply means that the bots (or humans) are able to answer your captchas.
There's nothing we can do in JFBConnect to fix this. What I'd recommend is using something like
SpamBotCheck
which doesn't require captcha at all and instead looks up the user's IP or email on remote services to check if they're known to be spammers and denies them that way.
I hope that helps,
Alex