I know it's ugly and not legal URI syntax, but this could cut N GETS into one, where, as one possibility, the server could compile the path into the separate requests (if necessary). Then again, I guess this transformation could happen client-side.

It seems like repeated filtering is always involved in getting some desired resource; it would be great to get this with one request. Perhaps that newcomer GraphQL addresses this by design.

Often I wonder if the best HTTP API would involve the remote execution of some non-turing-complete query-language guaranteed to terminate. Just select, filter, basic "joins", etc.