Apple has come up with a plan to battle these scammers and has changed its policy as discussed in the Developer Portal. Starting immediately, app screenshots will be locked in to the images used at the time that Apple puts its stamp of approval on the app submission. This rule would prevent those naughty bait and switchers from turning a pedestrian app into the hottest video games available. And while Apple does pull the app and refund the money once the ruse is discovered (which it always is), the policy change is sure to weed out some of these phoney apps in advance.
source: Apple via TUAW