YAML isn't a particularly good config format either, since it has a lot of unnecessary complexity. For example, bare words are strings, but some bare words, such as "true" are booleans. Which wouldn't be so bad, but did you know that "yes" and "no" are also booleans? I've gotten YAML files from an i18n-system that screwed this up in a pretty bad way.

In fact, YAML is a superset of JSON, and any valid JSON is also valid YAML. This becomes more obvious when you realize you can put any JSON objects inside of your YAML document and any YAML parser will correctly deserialize it.