That's why I would not consider investing energy/money/time in developing an app/application/client of a proprietary third-party platform: they can lock you out

That's why I would not consider investing energy/money/time in developing an app/application/client of a proprietary third-party platform: they can lock you out any time, sunset the platform (seen with Google Search API) or decide to compete with you (seen with Facebook regarding games). Open standards, open-source based or decentralized platforms, or your own platform are the way to go (I'm talking here from the dev perspective, not from the end user perspective - but proprietary sites are equally annoying for end users when they get discontinued. Making a one-time exeption to my self-hosting preference, I had a blog hosted at Posterous until Twitter acquired them and they shut down).