Great quote from Steve Yegge (in a much longer transcript on javascript):

JSON and XML are muscling in on each others' space, and there are bristles, OK, and it's so silly! It's silly. The whole thing, right? I mean, XML is better if you have more text and fewer tags. And JSON is better if you have more tags and less text. Argh! I mean, come on, it's that easy. But you know, there's a big debate about it.