I bet very few people would bother adding metadata without a concrete use.
This whole discussion about meta-data sounds eerily familiar...
From: http://en.wikipedia.org/wiki/SGML
"As a document markup language, SGML was originally designed to enable the sharing of machine-readable large-project documents in government, law, and industry. Many of these documents must remain readable for several decades — a long time in the information technology field. SGML also was extensively applied by the military, and the aerospace, technical reference, and industrial publishing businesses. The advent of the XML profile has made SGML suitable for widespread application for small-scale, general-purpose use."
So now XML isn't light enough... :-)
Mark W.