I don't think it's really like groupon. The core of groupon isn't a deal, it's a surge of attention pushed out to a large group of subscribers.

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.