Brian Doherty @ reason.com says:

Defending non-voting in bars across this great land, I often hear the ultimate "shut up"—that if you don't vote, you have no right to complain about politics or society. The reality is the exact opposite: By voting, you are playing a game whose rules are that the majority vote winner gets to control the reins of government, in all its unspeakable power. If you complain about the results of the game you chose to play, you're just being a sore loser—or winner.

Here's the whole of it:
http://www.reason.com/hod/bmd110204.shtml