Yeah, it definitely sounds FR-worthy to allow business owners to choose how they'd like a FB visitor to "earn" their free wifi. Hey, I'd be willing to sell my soul a bit for my favorite coffee shops to upgrade to Ruckus!
At any rate, with that said, I'm sure you can use the existing Captive Portal / Hotspot API infrastructure to implement something like this yourself. It would require more web app coding on your side, and isn't turnkey.