This seems like 'Foursquare meets Groupon'. It will be interesting to see who gets assimilated.
Your point about assimilation deserves some discussion though. I don't think facebook wants to buy any location based companies, it's in a good position now to just be the underlying platform. They don't have a whole lot to gain by buying these companies anymore.
But deals and offers is mostly a sales and support problem, and that's the kind of thing facebook /might/ build through an acquisition.
Also, while the business model is not anything like groupon's, to the consumer it is similar. Just another way to get a good deal.
On a related note (full disclosure), I worked with Signpost when they were Postabon, and I got the question "You mean like Groupon?" 100% of the time until I started differentiating the two in my initial explanation.