Defeating CAPTCHA's with porn:

Spammers have created a Windows game which shows a woman in a state of undress when people correctly type in text shown in an accompanying image.

The scrambled text images come from sites which use them to stop computers automatically signing up for accounts that can be put to illegal use.

By getting people to type in the text the spammers can take over the accounts and use them to send junk mail.

(Via Bruce Schneier.)