Location Proofs
The more businesses reward me for showing up at their establishments, the more likely it will be that a bad guy would want to pretend that they were there to garner those rewards.
I came across a very interesting paper that proposes the notion of 'location proofs.': Enabling new mobile applications with location proofs)
From the paper: "Location is rapidly becoming the next “killer application” as location-enabled mobile handheld devices proliferate. One class of applications that has yet-to-emerge are those in which users have an incentive to lie about their location. These applications cannot rely solely on the users’ devices to discover and transmit location information because users have an incentive to cheat. Instead, such applications require their users to prove their locations. Unfortu- nately, today’s mobile users lack a mechanism to prove their cur- rent or past locations. Consequently, these applications have yet to take off despite their potential." (from Enabling new mobile applications with location proofs)
I think something like this is inevitable, but it will have be invisible because it's too geeky..