Is this ZDNet?
Protocol buffers are just silly - you have XML when you need a self-describing document with a schema (pick a style) and JSON when you don't. If you're going to need performance, stream it - I mean this guy (at Google) is comparing a heavyweight DOM parser with his PB implementation! If you need smaller size, down the wire, GZIP or RLE (for speed) it then just SERIALIZE THAT if you're trying to do some binary transfer!
The whole point of XML was that it was text based. XML is used as a first class citizen in several frameworks for creating data access classes and even as intermediaries when creating data access models. JSON is a first class citizen on the client side so why create a new bleeding format? Answer: who cares? A file format is a file format is a file format. If you're sitting that far on the bleeding edge you're bound to get your bollocks sliced off sooner or later - so if you are doing any kind of software development which makes money then this API is probably not for you - for the next 24 months at least.