Just as a side-note -- I've had requests from others to add a switch to turn captcha off!  Different strokes I suppose. 

I've read Phil Haack's posts on honeypot captcha and I think this would also be valuable. I am open to adding something like this and I look to the community to gauge the level of interest.  That you're bringing it up means it's important to you.  I'll add it to the list of requests

An Image captcha option is not a priority at this time.  The textual-question one works well and image-based captchas don't work well for folks who turn off images as well as accessibility problems for folks who access the website through browsers such as lynx.  For these reasons, I've shied away from implementing an image-based ...