Not to pick on you in particular, Slothrop, but isn't it a logical error to see voting in a safe seat as being less 'useful' than the others - similar to thinking that a win late in the season, to take the league, is worth more than one earlier on?
Another way of looking at it would be to consider that the losing votes in a marginal seat would be worth less than those in a safe seat, as you have a larger number of voters whose preferences are 'ignored.'
Or, alternatively, a 'safe seat' is nothing more than an overwhelming show of voter power.