> However, you built your something with a foundation out of your control.

The trouble isn't this necessarily; a lot of business models don't exist unless another company does. The App Store is a good example of this; if Apple just disappears then so many other businesses disappear with it.

The trouble is the fact that the relationship between these two parties is so one-sided. Unless these third party Twitter clients have some sort of contractual foundation to stand upon, then yeah, what they've enjoyed so far is basically akin to an ad-hoc, at-will support, that can be terminated at any time with no notice, for no reason.