Well, at the point where you want to make a 'public' API for any sort of service, one would hope you know enough about the problem you are trying to solve to be

Well, at the point where you want to make a 'public' API for any sort of service, one would hope you know enough about the problem you are trying to solve to be able to provide a nice API? Also, for a 'public' API, I would definitely go for a bit more abstraction, and would attempt at making as future proof as practical. Of course you can ALSO fall on the other side of the fence with that by providing an API that is so 'future proofed' that they become next to unusable without another API on top! Apple was the Grand Specialist at that in the 90's. My reply to the post two level up was more regarding /internal/ APIs, the ones you create on top of an existing library for example, to integrate into your own systems.