"logged-in only" editing

I am strongly in favor of anonymous and pseudonymous editing, but I think allowing unregistered users to create articles is a drain on administrator time and should be avoided.

There are disadvantages to editing as an IP, but there can also be advantages. Most of them are of the "no pain, no gain" variety and have to do with the ability to determine truth without knowing authorship. Also, privacy is important for people who have been threatened.