I like that analogy. When designing an API I try to avoid over-engineering for use cases that might exist in the future, but at the same time I do try to make it hard to end up with invalid states. You don't need to wait around for a user to send invalid data before designing to prevent that.

So I guess the question is whether, in this analogy, net neutrality is about use cases or about valid states? Personally, I see it as more of the latter.