Reasons why voting Libertarian (or another third party) is not "wasting" your vote.

[Final-Fan]

Jumpin said:

[In U.S. national elections, third parties] are just garbage cans for votes.

Harsh but true most of the time.  However, it should be remembered that every few decades a third party gets real national attention with some platform or other.  What I believe usually happens is that one of the two main parties changes itself to accomodate the third party's platform and thus win over voters who were voting for that third party.  I believe this happened in the aftermath of the 1992 election (Ross Perot's budget reform proposals). 

Perhaps the most famous example is the several third-party candidacies in the mid-twentieth century that got electoral votes.  I refer to the various political parties representing the segregationist South in its opposition to efforts to end segregation and other discrimination against blacks.  The 1948 election literally saw two different candidates running under the Democratic ticket.  (In some Southern states, Strom Thurmond was able to run under the Democratic Party name but in most he was obliged to run under a third party ticket instead of using the Democratic name.)  Pro-segregation third parties also got electoral votes in 1960 and 1968. 

It is common political knowledge that these voters were in general successfully courted by the Republican Party ("the Southern Strategy"), and many Southern Democratic politicians of the time defected to the Republicans as well, including the aforementioned Strom Thurmond, whose long tenure as a Republican US Senator lasted until 2003.