JSON parsing is a minefield, especially in cross-platforms scenarios (language and/or library). You won't encounter those problems on toy project or simple CRUD applications. For example, as soon as you deal with (u)int64 where values are greater than 2^53, a simple round-trip to javascript can wreak silent havoc.

See http://seriot.ch/projects/parsing_json.html

Protobuf support for google's first-class citizen languages is usually very good, i.e. C++, Java, Python and Go. For other languages, it depends on each implementation.