Now, I'm not going to discourage you from voting. As long as you have an ounce of knowledge that comes from credible sources, it's in the advantage of the country for you to vote (and if you're voting based on campaign ads / what your friends are voting, SHAME ON YOU).
Statistically speaking, the chance that your vote will change the election is slim-to-nothing. XKCD provides a nice run-down of the probabilities. Knowing this, why do so many people vote?
The power in voting comes from the illusion that your vote matters. If voter apathy prevents one person from voting, then there's virtually no harm done.
The damage happens when a large group of people suddenly decide (logically so) that the gas it takes to drive to the voting place and the hours of time wasted at the voting booth isn't worth the minuscule chance that their vote will be a determining factor. It's then where you'll have some problems. One vote will not make a difference, but ten thousand votes certainly will.
So the next time the election rolls around and people try to guilt you into voting, remember this: It's okay not to vote. Just as long as you encourage everyone around you to vote.
And just as long as not too many people read this blog post.