By contrast with the globally interoperable legacy telecom world, web-based communication services, which become front line actors in the interpersonal communication field, are founded on "walled garden" approaches. With the emergence of full-web technologies, driven by WebRTC, it is envisioned that these services can be made compatible and interoperable, possibly thanks to new enablers provided by telcos, to the benefits of consumers who would enjoy seamless reachability of their entire contact lists. Given the diversity of the concerned actors and their goals, we believe it is timely to review the question of service interoperability. We discuss the various levels of interaction, review benefits and hard issues, and make a proposal for a workable solution.