When inserting new documents in mongodb, ids don\'t look like ObjectId and instead they look like an object.
\"_id\" : {
\"_bsontype\" : \"ObjectID\"
I was having the same issue here: ObjectID not storing hexadecimal value
It's definitely an issue with environments and something strange with the brew installation of MongoDB. I found that uninstalling from brew and reinstalling manually solved my issue. http://docs.mongodb.org/manual/tutorial/install-mongodb-on-os-x/
While I didn't figure out from a code/technical standpoint why it is returning the 12-byt BSON ObjectID rather than the Hexadecimal ObjectID... uninstalling MongoDB from brew and reinstalling it manually solved the issue.