I have a ton of ideas that involve Foursquare.
I think it could be huge down the road if more people, business, and yes even churches start to use its power.
Competition is a powerful thing. Ask any guy (and even you girls) that play Call of Duty online why they play? I would go as far to say that they play more for the competition of gaining more rank and to get better prestige. Its the power of identity and being able to say you are better then someone else. Foursquare is a tool that almost promotes that in some way or another, at least the competition piece. Check this info-graph below and see the potential and the growth over the last year.
I will write more on this later.