Dave,
If non-voters can't be arsed to participate, then they've got nothing to complain about.
Because if you're a non-voter you can vote your conscience and not worry about tactical voting, because you already don't mind who wins. That way minor parties have a chance of becoming mainstream - which tactical voting in first-past-the-post elections makes much harder.
Society works because large groups of people cooperate. That means sometimes you have obligations. Voting is a pretty basic part of democracy, and democracy is the worst system in the world, except for all the others.
