Services piggybacking on other services.
“I like what Gogobot is doing; leveraging check-in data and turning it into more of a lasting resource. Gowalla also tries to do some of that with its own passports. But with many location-based services, check-in data isn’t as organized or designed to be used as a broad travel tool.”
Gogobot most likely doesn’t pay for this access either, even though they use it in bulk. I’m just guessing though.
That’s the crux of this industry. It might not be the core provider that actually gets the main dough. It’s the one that presents the best ads and deals to its members.