"I find that the quality that seems to define beauty, at least for me, is MYSTERY"
Well, that may be true - but every captcha I have ever seen has been a brain-bending mystery.. and to me, this particular mystery is utterly devoid of beauty!
"but that does not mean that all that is beautiful is necessarily simple"
I Certainly agree with that!
Fred.
What about, where the "Welcome FredM!" appears at the top of the page, an image is inserted containing a password for the day..
Or how about members getting a password specific to their account once they have proved themselves, and this being a 'skeleton key' which works for them instead of the captcha?
Or perhaps you could just charge new members a fee or deposit before they are allowed to post.. say $5.. that may stop a load of students from joining, which is sad ;-).. It would certainly stop spammers, but would not (I think) stop people seriously interested in theremins from joining.