There's word that if an app is unapproved and removed from Marketplace for Mobile, Microsoft's version of Apple's App Store, then it will also be removed from all users' devices. No information on whether that includes refunds for paid apps.
According to Boy Genius Report and PPC Geeks, "Microsoft has confirmed the existence of a ‘kill switch' for apps". The current explanation is that if at any point in time an application is unapproved and removed from the store, it'll also go bye-bye from your headset. This is a bit disconcerting when we think about some of the things we've seen with Apple and what we know about Google. Hopefully Microsoft will play nice and have a reasonable process. Like letting us keep the apps we download. [PPC Geeks via Boy Genius Report]