I was at a startup in 94/95 where we made something a lot like protocol buffers, with a multi-platform, multi-language (Java / C++ / COM) API on top of it. Was very friendly -- very JSON-like -- and worked really well, up to tens of thousands of messages a second through then developer-class Pentium boxes.
I think you can still go fast without being nasty. Whether there is money in it is another question.