What do you think the donkeys are thinking when they limp on a short stack? Sometimes, it is, "I'd like to see a cheap flop, but I'll fold to a raise." Often, however, it is more like, "Finally, a good hand. But damn, I don't want to bust out before the money! I better just limp, and then if the flop is scary I can get out." In the latter case, the donkey cannot be pushed off of her hand pre-flop, but will gladly fold AK if rags flop, considering herself clever for avoiding a near bustout. I like to lead out any flop against this kind of donkey.