I've been fascinated by the "spam art" that manages to get through the gauntlet of spam filters at work.

It has been fun to watch the cat and mouse game that is played between the spam filterers and the spammers. The spam filterers develop methods to use OCR to scan images, and the spammers develop methods to subvert the OCR.

I just had this realization: the spammers are doing free testing for making CAPTCHAs.
One only needs to check their inbox to find the latest in OCR avoidance techniques!