JSON is actually UTF-8/UTF-16/UTF-32.

I much prefer requiring only UTF-8. UTF-8 is enormously more common and a single encoding is a significant simplification; the gains from UTF-16 are much reduced by the fact that markup almost always uses ASCII characters.  If an implementation wants to support UTF-16, it should be free to do so, but as a requirement it is on the wrong side of the 80/20 line by a long way.

James