Hi Gavin, Mike and co

Is there a strong driver behind the choice of Google Protocol Buffers for
payment request encoding in BIP-0070?

Performance doesn't feel that relevant when you think that:
1. Payment requests are not broadcast, this is a request / response flow,
much more akin to a web request.
2. One would be cramming this data into a binary format just so you can
then attach it to a no-so-binary format such as HTTP.

Some great things about protocols/encodings such as HTTP/JSON/XML are:
1. They are human readable on-the-wire. No Wireshark plugin required,
tcpdump or ngrep will do.
2. There are tons of great open source libraries and API for parsing /
manipulating / generating.
3. It's really easy to hand-craft a test message for debugging.
4. The standards are much easier to read and write. They don't need to
contain code like BIP-0070 currently does and they can contain examples,
which BIP70 does not.
5. They are thoroughly specified by independent standards bodies such as
the IETF. Gotta love a bit of MUST / SHOULD / MAY in a standard.
6. They're a family ;-)

Keen to hear your thoughts on this and very keen to watch the payment
protocol grow regardless of encoding choice! My background is SIP / VoIP
and I think that could be a fascinating use case for this protocol which
I'm hoping to do some work on.

Best,
Richard