Any service where you also control the client doesn't really benefit from the use of SSL certs issued by trusted public CAs, other than the simplicity of doing

Any service where you also control the client doesn't really benefit from the use of SSL certs issued by trusted public CAs, other than the simplicity of doing things the same way you always have. Imagine a file storage service accessible via a desktop client, mobile client, API and web. You can't get around using trusted public CAs for API and web, but the desktop and mobile clients could only trust your own CAs with no loss of functionality. I think the major stumbling block is that the best practices for running a CA aren't well known or broadly disseminated or easy to follow. If you're developing a system that makes it easy to securely manage a signing key, and otherwise do the right things, that would be sweet. Not sure that there's monetization potential there though.