[guideamigo]

This is the only example everyone points out against yaml.

For Json, there are several such syntactic problems. Unnecessary double quotes and only double quotes everywhere. No dangling comma.

[msm_]

These are different kinds of problems.

JSON is (arguably) too strict. YAML is (arguably) too loose. One is better for machines, the other is (usually) better for writing by humans by hand. There's no perfect compromise for every use case.