This story was techmeme’d but the ComputerWorld article fails to mention the potentially viral nature of this sharing feature.  Microsoft is a pretty strategic company, but I can’t be sure they had this in mind:

The feature is primarily aimed at customers who own multiple Windows smartphones and want to use the app on each phone, but it could also create a very interesting viral component, in which users could swap apps and encourage each other to download new ones.

via Microsoft’s Mobile Marketplace Will Have A Viral Component; Windows 6.5 Is Done | mocoNews.