[Dunkman]

If you are behind you're not getting to a showdown cheap, because 1) it's gonna look like you're trying to draw cheaply and 2) he's gonna be hammering it trying to keep you from drawing out on him. If you're ahead then he's most likely drawing (or folding if you bet) and all you do by betting small is give him great odds to draw at his hand, and encourage him to make semi-bluffs, which he will be less likely to do if you attack hard, and which will look a whole lot like a made hand if he makes them.