Is This Driving Incremental Revenue?

So I went to lunch with my daughter today.  We were out and about and she loves Tony Roma's, saw that we passed one and asked if we could go to lunch there.  When walking up to the door there was a "check-in with foursquare" sign on the front door.  So I did.

Mind you I was already there, already made my decision to eat there, was going to pay full price before I saw this sign.  I checked in and they gave me 10% off of my meal, for essentially doing what I was already going to do.  So why is this a good strategy?

I understand the whole social aspect of this check in.  This goes to all of my "friends" and they get to see I ate there.  But how many of my "friends" are paying attention to what I am doing, aside from those stalkers I have, by the way, stop reading this, but I digress.  How many people am I really influencing, enough to make up 10% for a meal I was going to pay full price?  I don't see it.  That is a lot of cost to overcome to drive something that can't be measured.

Am I crazy?  I just don't see this as a good business decision.  Just my thoughts.