[hvdijk]

I assume and hope that they do not, if there is no rule stating that they are invalid. There are valid reasons for JSON to massive keys. A simple one: depending on the programming language and libraries used, an unordered array ["a","b","c"] might be better mapped as a dictionary {"a":1,"b":1,"c":1}. Now all of your keys are semantically values, and any limit imposed on keys only makes sense if the same limit is also imposed on values.

[forty]

Yes absolutely, in practice the limit seems to be on the document size rather than on keys specifically. That said it still sets a limit on the key size (to something a bit less that the max full size), and some JSON documents valid for a given JSON implentation might not be parsable by others, in which case the Yaml parsers are no exceptions ;)

I'm not even sure why I'm playing the devil's advocate, I hate Yaml actually :D