This isn't a huge deal, but I was approached by colleagues/friends to build an app using their new API. There was some potential for pecuniary gain for me depending on app usage. I spent a considerable amount of time polishing the mobile app, based on my assumption that, having been approached in a serious way, that the company would not suddenly shift focus and abandon the API. I wasn't even given so much as a heads up that the API was dead even though I had an app in production that relied on it...

For the most part, building the app was a learning experience which I enjoyed, but I don't think I'd have expended all the effort if I knew that the company wasn't as serious about the API as their reaching out to me clearly indicated.

How, if at all, would you react?