Referees: Really influential or not?

Given Fergies comments again about refs, how much do we really think they influence the game?

I've seen 2 different sites quoting andre marriner and mark halsey as refs for today's game. One is bottom of the league for cards and the other is near the top and has sent Glenn Johnson off before in a fixture between us and Stoke.

Does a card happy referee mean a spoilt or a well controlled game?