[Answer]-Django and mongo really schemaless

From mongoengine documentation:

MongoDB is schemaless, which means that no schema is enforced by the database — we may add and remove fields however we want and MongoDB won’t complain. This makes life a lot easier in many regards, especially when there is a change to the data model. However, defining schemata for our documents can help to iron out bugs involving incorrect types or missing fields, and also allow us to define utility methods on our documents in the same way that traditional ORMs do.

http://readthedocs.org/docs/mongoengine-odm/en/latest/tutorial.html

My hint is use data models when you can and don’t use them when you can’t