Right, but what I meant was triadic closure.

I can tell my friends to use this, but since I can already communicate with them through existing services (which may include geolocation like fb's find friends nearby or highlight) there's no real value there for me.

The value comes from talking to people who may not be on your social network (e.g. all of the use case examples on your page should be directed at as big a local audience as possible).