How to profit from spam

This just in from Boing Boing

David sez, “A fellow on the CISSP mailing list set up a simulation of a portfolio whose strategy was simply, sell short every stock he got a spam about. He ‘made’ $8K in two weeks.”

Now, why didn’t I think of that? (Hint: What’s the opposite of Schadenfreude?) (Oops: Wikipedia provides the answer: mudita.)