Regarding:
http://docs.mongodb.org/manual/faq/storage/#what-is-the-difference-between-soft-and-hard-page-faults

Not sure if we really need this. As far as I know, Mongo will not hit soft page faults on data files (at least on modern hardware).

Regarding:
http://docs.mongodb.org/manual/reference/glossary/#term-page-fault
I think this should read "... has moved to disk." instead of "... has moved to virtual memory."