Should You Ever Resign?

I've only been playing chess for a few months and while I have resigned in the past, I stopped doing it; even if I'm getting trounced.  There are several reasons why: I'm learning from my opponent; I never want to get stuck in the situation again and if I do how do I get out; I may be able to still create some threats and throw my opponent off; I may be able to get enough pieces that there will be insufficent material and I'll only lose one point; stalemate; I've noticed that I sometimes my opponents pieces will work against them creating a trap and so I may not need what was lost although it would be nice to still have what was taken; my opponent may make a mistake; you never learn anything from quitting.  Perhaps the biggest reason I see for not resigning is, if the game is over where is the crime in just resigning one move away from checkmate?  Now, I consider resigning or abandoning the game one move away from checkmate a really weak move; a move of cheapskates.  But if the game is over what is the difference between one move or two, or three or four?  Get my point?  Checkmate was still going to happen.  Whether it's three or one move away it's still a weak move yet I hear GMs, FMs, IMs, NMs, the masters say, "My opponent should have resigned; It's basically over for white; It's basically over for black; why continue; etc."   Maybe at the master level, which I am far from, it's acceptable because in order to get to that level they learned not to make mistakes so checkmate is inevitable.  But everyone has an off day and mistakes can happen.  Either way, from what I've seen at that level of play it isn't a question of whether a blunder will be made but rather will the best move be made and if it isn't, if there's a magin, an edge then the tables can turn.  Basically, I can think of more reasons for not quitting then for quitting, so why quit?  Why resign?

So what's your take on resigning?  When is it resigning acceptable?  Is it ever acceptable?