Saw a headline today on this interesting social-engineering approach to trick users to decrypt PGP messages through a common email software flaw and send it back to the sender. Here's a link to the story on CNET:

http://news.com.com/2100-1001-949368.html?tag=fd_top

I had originally posted the entire article from another site without thinking. Sorry about that. Hope the URL-only is satisfactory.