Edit: I have been looking for reasonable configuration file formats for a while. Json actually has pretty bad human-readability at any scale because of its quoted key-values. Yaml is easily readable but when a user tries to change anything, things go to hell. The humble ini-file has won so far. It's limited and not fully standardized but it is human readable and human writable. I'd love see something better but human readability/writable is going trump all sorts of cleverness.
Edit2: From http://en.wikipedia.org/wiki/YAML "The specific number of spaces in the indentation is unimportant as long as parallel elements have the same left justification and the hierarchically nested elements are indented further."
Yeah, a user of your software is going to be able to understand when they mess up on that rule, riiiight. Screw Yaml.