Earlier quoted context omitted.
But the posters above you said that JSON and JSONB types in Postgres, and functionality around them, eliminated the need to use other databases for document type data. What you are describing can be done with PostgreSQL. One thing that is missing is better client libraries that make use of those data types. Morphia wins for now in that regard.
My claim wasn't that it didn't fulfill their needs, it was that it doesn't fulfill all needs (gamedev is one example that I'm familiar with). Postgres storing JSON types != All mongo functionality I'm sure I could achieve everything I'm doing in mongo by some roundabout way in Postgres, but if you're doing a large amount of reading/modifying partial fields within JSON structure, it's the exact use case for mongo.
that said, I actually use partial JSONB updates on a regular basis, but I tend to use PLV8 to do the heavy lifting.