If you have even a passing interest in the business of video games then you've certainly tried your hand at least once trying to predict the potential sales of a game you felt convinced was going to do particularly well (or poorly).
The SimExchange creates a free virtual futures market to allow the would-be Warren Buffet's of the videogame space to safely try their hand at predicting top-selling titles.
Publishers, I'm sure, will also be keeping an eye on this service to see how closely the Wisdom of The Crowds mirrors real life for actual shipped titles and invest their trust in the future predicting capabilities of the service accordingly.
For now some titles' sales projections seem to be woefully exaggerated (as much as I'd like to believe it I don't think Rival Swords for the PSP will sell 400k+ units) so I'd take the whole thing with a grain of salt.
A very cool service nonetheless! Worth checking out.