> if you utilize a third-party API for the core of your app, you are at their whim

More than that, if you aren't paying for use of that third-party API, the people who run it will not care about you, and will think nothing of shutting you down.

I think Yelp handled this poorly, and Restaurants was probably a net positive for their business -- a positive that they were getting for near-zero cost. It's a shame that companies are so short-sighted like this.

But ultimately if you build on top of someone else's platform, with no backups and no alternatives, it's not really truly your app.