Applications sharing in OS3, could that be possible?

News has just come out that with the new iPhone 3.0 software it may be possible for developers to allow software they write to be shared to another users device.  We are not sure how this will work or function, but this could be a very interesting marketing system to pass and share apps.  Google has been looking into this method of sharing and recommending applications, and until now the only option has been a crude send recommendation button that would trigger a simple email to be sent out with details about the application.  It may be also possible to earn referrals of some kind down the road, that could really produce application sales.  The main question would be how would Apple take its share of the pie if the application can be transferred from one device to another?