Apple to Lock Down Screenshots in App Store
Apple, App Store
Just posted on the Apple developer portal is word that "Beginning January 9, app screenshots will be locked in iTunes Connect once your app has been approved. New screenshots may be uploaded when you submit a binary for an update to an existing app or a new app. For more information on capturing and using screenshots, read the Xcode User Guide."
This is very good news because previously scammers could swap out screenshots later, as a way of pretending their apps had features (or were other apps) that they didn't.