[Edited by Chingy-X, 11/5/2009 1:59:44 AM]
The risk/reward figure for a bank is not very good. You generally don't find more than a few thousand dollars that the tellers at a branch bank can access and your risk of being caught is almost 100%. Whereas you could knock off a couple of liquor stores, get the same amount of money and have very little risk of being caught.
Suffice it to say that evil geniuses don't rob banks--they set up elaborate stock market ponzi schemes.