Good comparison of JSON and XML

XML.com: JSON on the Web, or: The Revenge of SML provides an interesting comparison of JSON and XML and their relationship to YAML (popularised in Ruby on Rails configuration files). JSON seems to obviously be preferable when one of the parties can execute Javascript, read it directly into Javascript runtime, walk it like any javascript object tree - no mucking around with E4X. You can also convert back and forth between JSON and XML, which is nice. It's also clearly useful in loosely-typed situations. Where the information being sent over is structured but not necessarily validated, so nice for tightly coupled applications.