Popular room rental service AirBNB does not yet have an official AirBNB API. But signs point to one's existence, as well as an affiliate plan in place to pay developers for reservations booked through the API. If the company sticks with the plan as written now, developers will be able to make up to 10 million API calls per day before contacting AirBNB.
Though a few shopping APIs are some of the earliest examples we have, their popularity has continued to grow for a simple reason: there's an obvious revenue model tied to them. When developers use one of the 82 Shopping APIs in our directory, that can mean money in the pocket of the API provider. And, by virtue of various affiliate and revenue-sharing programs tied to many of these APIs, it can also mean money in the pocket of the developer.