The DIY Economist

FAS and FAZ are the 3X leveraged financial funds - they move 3x the rate of the underlying, with FAS moving 3x in the direction, and FAZ moving 3x in the opposite direction. I made a PDF cheat sheet that hopefully demonstrates why shorting both FAS and FAZ will likely result in a suboptimal play over buying both given approximately normally distributed returns:

http://diyeconomist.net/files/FAS-FAZstraddles.pdf