To vote or not to vote? What exactly is the question?

After this grueling election season, a lot of people are expressing surprise that so few of their fellow Americans chose to exercise their right to vote.  (According to reports I have seen, voting was at a 20 year low in a presidential election, which is bad, even for the United States, which typically has a low turnout, anyway.)  I have seen a lot of disparaging remarks about not voting, and I think they have missed the point. We also have a right not to vote, and it can be a choice of honor, a choice of exasperation, a choice of civil disobedience, a choice of protest.