Why third-party votes matter more than others

        When I tell people that I will probably vote third party, I typically get an eye-rolling or a "Okay, just throw away your vote" sort of response. To me, this is a very short-sighted perspective.
As with last election, the country finds itself asked to choose between candidates who are nearly identical on all important issues (though not comprehensive, this video gives a pretty good demonstration of the fact: http://www.lewrockwell.com/blog/lewrw/archives/118098.html). 
When I raise this point and get at least partial agreement, there are three responses I hear:

1. Vote for the lesser of two evils: Basically, they say that if we can't get someone good, at least vote for the best candidate who has the chance.

2. Don't vote: This is advocated as a moral stand where you are not giving your consent to either of the big candidates. Even though several people that I otherwise respect advocate this view, I have never heard a convincing case as to why this will actually make any difference, so I don't support it, myself.

3. Vote third party: Yes, I am aware that this won't change who wins the current election, but does that mean it doesn't have any effect?

If you always vote for the big two, then your vote is taken for granted:
Democrats, will you ever vote Republican? Republicans, will you ever vote Democrat? I didn't think so. That means that your vote is free. That means that your party can do whatever it wants, break whatever promises it makes, and even follow the exact same plan as his predecessor from the other party (like our current president has done) because they're secure in knowing that you'll continue to vote for them.

A third party vote says "Neither of you are acceptable to me. This is what it would take to get my vote." Sure, if the Libertarian Party (or whatever group you like) only gets one percent of the vote, they can be mostly ignored, but what about when they get five percent. Many presidential elections could be turned with a five percent change in the vote, and suddenly, the Libertarian demographic would be one that the big two would start trying to appeal to. Instead of deciding whether to increase spending by 1.4 trillion or 1.6 trillion, they might actually discuss reducing spending. Instead of quietly ignoring the fact that when two countries are at war, we often provide money to both, the idea of giving money to neither might actually be raised.

Ultimately, no matter how you vote this election, the country will move in generally the same direction for the next four years. But with a third party vote, you just might be able to have a little influence in the years after that.