I would hope that if the maintainer of an api was planning on making a not-backwards-compatible version change they would put a hell of a lot of time informing

I would hope that if the maintainer of an api was planning on making a not-backwards-compatible version change they would put a hell of a lot of time informing people about it. That way, people who need to stay on old can add in the string, and those who can adapt will. The v1 just doesn't seem to belong in that part of the url to me. Maybe if you had v1.api.example.com/coolstuff/1 - that I'd be more comfortable with.