Let the hating begin.
Dave Winer finally has an actual look at the JSON format, and to his horror, finds that "IT’S NOT EVEN XML!" Ah, the hideous, "blood, guts, veins in my teeth" humanity of it all. In summary, here are his impressions:
No doubt I can write a routine to parse this, but look at how deep they went to re-invent, XML itself wasn’t good enough for them, for some reason (I’d love to hear the reason). Who did this travesty? Let’s find a tree and string them up. Now.
Seriously, If you just want to serialize some data (and of course, if you're not one of the inventors of XML-RPC), there are lots of good reasons you might prefer JSON to XML.