nosism (NO-siz-em) noun
The use of 'we' in referring to oneself.
[From Latin nos (we).]
As it's often used by editors, it's also known as the "editorial we".
It's also called "the royal we" owing to its frequent use by royalty.
Mark Twain once said, "Only kings, presidents, editors, and people
with tapeworms have the right to use the editorial 'we'."
(from today's Word a Day. Archive here).
Dean and I use the "royal we" all the time at home, when we are being silly. But we use it to replace "you" rather than "I." For instance, "How would we like our eggs this morning?" and "Did we just fart?"