I'm all for super-verbosity in useful information and flexible structure, but XML is also super-verbose in terms of redundant markup. Compression helps a bit, but it still costs processing power for no real reason. See the good ol' S-expressions vs. XML discussion, recently reincarnated as JSON vs. XML.

The deicision was a big step forward; however, moving off XML to an equivalent but less verbose (in number of meaningless bytes) format wouldn't hurt. All else being equal, it would be less electricity wasted on reading and sending things over the wire, and also more human-readable format. See also: SEXP vs. XML.

This argument applies the more, the bigger markup-to-data ratio is.