Forums are communities, after all! If someone has been on a forum for a long time, then they should feel akin to the community; if they don't, then there is a problem.
Interesting question and not something I had thought of before. I think theezy put it very well. However, I'm not sure that anyone on a forum should really say we when talking about his / her opinions. Everyone has their opinion and any one person's opinion does not necessarily reflect that of everyone else in the community.
On a slightly related note, small business owners will often say "we" when talking about their one person business, to give the impression that the business is bigger than it actually is.
I don't like backseat moderators but I dont mind people saying "we"
Members make up the community, as a community member they are part of the "we"
:lol: