So I had a similar idea about six months ago. Briefly start working on the app when I was informed by a lawyer friend of mine that most states had laws against advertising drink specials.
Interested if you have looked in to this at all, especially because googling "laws against advertising drink specials" brings up this http://www.wtop.com/41/2821800/Vas-happy-hour-law-makes-some... as the first result.
On a broader scale I guess this brings up two points: 1) have the owners of this site considered this issue yet? 2) Is it sometimes better to just build it and worry about the legal ramifications later (to a point)?