For the brewery its the same benefits as gift cards: Not everyone that receives one will actually use the money. On top of that, free advertising.

And all you have to do to get these benefits is somehow integrate with twitter and a payment system. Which might be a tall order for a local brewery.

(Or is that easier to do than I think?)

Its not my area, so I don't know how easy it is to do, but I do think it could be a space for a third-party to step in. Someone figures out how to handle the twitter/payment side, reaches out to some local breweries/bars, takes a small cut of the money for each beer tweeted. Its not going to be a super profitable business, but it might be a fun sideproject for someone.

I forgot to add the 3rd benefit to the brewery is that I would assume, in general, when people stop in, they don't come alone, and they don't just have one beer and leave. Once they're in the door, they tend to spend more money.

You mean besides the business it would get?

Well, sure, they'd get business--that's the benefit.

But how easy is it to tie into twitter and a payment system? That'd be the cost.

Starbucks can distribute such costs (which may not be fixed, but certainly won't grow linearly) across a larger number of stores than your local brewhouse can.