Just out of curiosity, do other objects that get logged simply get casted to strings?

It's been some time since I saw the logger output for this bundle, so your example helped jog my memory.

I suppose the most preferable option would be to serialize the driver classes in the "strict JSON" format defined in: http://docs.mongodb.org/manual/reference/mongodb-extended-json/#data_binary (the `mongoexport` commands use that notation), but that would be outside the scope of this PR. Let's leave it as-is for now, then.