Traditionally, the term We is used by the royal family of any nation in order to signify that they are speaking for the entire country. The plural we indicates that their will is significant enough to singularly encompass the thoughts and process of an entire country.
Historically, the royal plural is always used when a King or Queen wants something, but often leads to trouble. Due to the special bond that a ruler employs with his or her people, signifying any sort of need has a tendency to cause effects in a very large section of the populace. The empathic bond to the countrymen of a nation was first established in the magic spell known as the Magna Carta. When the right to rule was established, so was the empathic link.
Early rulers frequently made the mistake of speaking too often about their needs, and thus dooming the entire country to strange desires that were frequently unfulfilled. One early example was brought forth by Queen Elizabeth I, who, as the first of a long line of royal persons, inadvertently caused terrible suffering with her early morning declaration:
Yawn. "We are *so* knackered. Where *has* that King gone? We wish we had a repeat of last night, we would find it most satisfying."
The entire pure country of England then suffered terrible atrocities, and gave birth to the start of gay men, cheating spouses, and terrible, terrible, UPN sitcoms. The world has never been the same.
The opposite of We is "Not-We", which also means people who aren't Doctor Who fans. Therefore, everyone who has used the word "We" to describe themselves must be a Doctor Who fan. This includes people who died before Doctor Who even was created. This proves that The Doctor has really traveled through time.