The discriminatorField and discriminatorMap options are ignored by both the YAML and XML drivers.
This mapping fails to store the discriminator in the type field and instead uses _doctrine_class_name as the discriminatorField the mapping also reverts to using class names.
I think that this is also a problem for referenced documents as well, as the code for the two is nearly identical.
I refactored addEmbedMapping and addReferenceMapping to call the same function addDocumentMapping
Commit can be found here http://github.com/dordille/mongodb-odm/commit/41ce2ee126ff7f82610130704dbec451384bfdd3