Backstory: While getting my car serviced I jumped on their free wifi and thought this would be a good place to exchange information.
The Idea: Access to customer's facebook information in exchange for free wifi.
Deep Dive: You would build a platform where the end users would be forced to create an account with their facebook account. My getting access to their facebook information, you could begin to a profile for improved client services.
Here's an example: A user signs up using your free wifi platform at a car dealership. Fast forward two months, they return to the dealership, and their phone auto connects to the wifi since they've already signed up. Sales people at the dealership get a notification of the user's proximity with their name, picture and brief summary of what they've done in the past two months. This would aggregate their facebook activity such as trips.
Validation: Getting businesses to know their customers even better is a huge win.
Monetization: You would charge customers a monthly licensing fee. You could have a base fee and charge more when they have more end users signing up for the free wifi. This model scales with the amount of data you need to hold and process.