Every time you version an API is an opportunity for your customers to consider a competitor.
I wish more people would ask how to avoid breaking changes in HTTP APIs instead of asking how to version them.
I wonder how many people realize that monoliths don't have to be big balls of mud?
Woot! HttpClient has made it to Github github.com/dotnet/corefx/…
With HTTP apis, you can either pay the cost of hypermedia or versioning. The difference is whether your customers will eventually hate you.