Google Protocol Buffers

Just found a good post by the Google Engineering team ranting about the historical context of Google Protocol Buffers.
My first reaction to GPB was - "Why on earth another binary serialization format"?
I think the reason behind the popularity of GPB has been its simplicity and ease of use. 

This site has an interesting discussion on comparing GPB to XML/JSON.  A few snippets from the site comments/discussions -

• A major difference between protocol buffers and JSON is that protocol buffers use a binary format, while JSON is plain text.  Because it's binary, the format is more compact and easier to interpret by a computer - which makes protocol buffers faster than JSON.
• Another reason GPB is so fast is that it uses positional binding. JSON is less bloated compared to XML (which is over bloated), it still sends the name of the attribute with each record. That creates an enormous amount of overhead. PB, on the other hand, uses positional binding and doesn't send the attribute names at all.
•  Binary protocols have to deal with portability issues like byte-order (little/big-endian) etc., there are advantages when it comes to parsing dates, timestamps, etc.