How might Google monetize Ingress?

The first question I had when I heard about the Ingress beta was: why is Google doing this?

Face it: there's a real dollar cost to anything Google does, so it has to do one of the following:

1. Generate more revenue than it costs
2. Enable other Google products and services to make more revenue than it costs
3. Improve Google's positioning relative to its competitors, in order to generally benefit their other products more than it costs
4. Meet one of Google's non-monetary goals in a way that they feel is "worth" the cost and is offset by other income

Ingress: Google's augmented reality MMO

Ingress logo

+Ingress is Google's new augmented reality game that's currently in beta. It brings together a few things: first off, it's Android-only at the moment and has a strong preference for players and developers communicating via Google+. This is an obvious play for increased adoption of both platforms.

That aside, however, Ingress is the first MMO that I've played where the first step is, "go outside," and as you play the game you get a definite sense that Google isn't kidding about that. The game won't allow you to set your phone in location debugging mode (I suppose if I loaded a custom Android image, I could defeat that, but realistically it would be self-defeating) and they choose locations that are artistic or historical for elements of the game.