[apefish]

One of the theories put forth is that the "superuser" ability could be activated/deactivated with a few lines of code or whatever.
This would mean there aren't dedicated full time superuser accounts but that accounts with that capability could be used from time to time and then made to sleep when not needed.

It doesn't seem far-fetched, but doesn't answer how many accounts there are like that or how many people know how to activate them.