Insert does not allow inserting records with fields containing keys with dots in them, which as I understand it is the correct behaviour. An upsert however, will perfectly happily do this:

> db.test.insert(

{ "test": 1, "te.st": 1 }

);
Fri Oct 22 17:13:37 uncaught exception: can't have . in field names [te.st]
> db.test.update(

{ "test": 1 }

,

{ "test": 1, "te.st": 1 }

, 1);
> db.test.find()

{ "_id" : ObjectId("4cc1b8371c20e0349d6568ad"), "test" : 1, "te.st" : 1 }