Geeeez, some people have just too much time on their hands:

In May 2005, a trojan called PGPcoder was discovered in the wild by Websense Security Labs. The trojan's purpose was to encrypt a user's files, then demand a ransom for their decryption. Although this scheme seemed novel, it is actually predated by over 15 years, by a similar scam in 1989. LURHQ's Threat Intelligence Group has now discovered a third such scheme involving ransomware which we are calling Cryzip.

 
Details here.