I noticed that in Fuerte mongoDB journaling is enabled, using up 1-2GB of disk space for no apparent reason. In Electric journaling was not enabled. Is this necessary? if not, can it be disabled?

It's possible that the change is caused by the version of mongo used. In Electric it was 1.8 and in Fuerte is 2.0. Mongo 2.0 enables journaling by default.

Maybe the best option would be to expose the "--nojournal" flag of mongo in wrapper.py.