This certainly isn't an original idea, but has anyone thought of spam blocking with turing numbers ?
Like what http://www.egold.com and other sites use ?
Essentially the same php tom foolery that photomatt uses for Titles could be used to make a turing number system.
The user would have to enter the number as it appears in the png picture or else the comment would get rejected.
The script uses md5_encode and _decode functions so the verify string is never found in the source code.
I mean ... this is not meant to deter an "attacker", but it would prevent spam "robots" and such. And a nice feature is that one could still allow anonymous posts and wouldn't have to review every one.
My blog is not ready yet, but feel free to play around with this system here:
I just had to change wp-comments.php and wp-comments-post.php around a little, as well as add a couple of hidden fields in the comments form.
If anyone is interested lmk and I can write up a better "how-to".