First, a little history. The framers set up a two party system for a reason; if the vote is split more then two ways there will be a leader elected by a less then 50% margin, which ultimately leads to divisiveness. Our system of governance is dependent upon the population accepting the results in the end.
As to whether a vote for a third party candidate is a wasted vote, I guess it comes down to opinion, although historically third parties have had little to no chance of winning, especially on the national level. So, looking at it that way, I would say it is a wasted vote. It comes down to being a protest vote and nothing else. Other than it makes the voter feel they have done their civic duty.
It would seem to me to be more effective if disgruntled citizens worked within the system to effect change in the party that more closely represents their philosophy rather than attempting to effect change through a candidate that won't be able to do anything to further the cause. I, for example, see much in the Green Party that I agree with, therefore I will work to get more people elected at the grassroots level that share that same agenda within the party I identify with. It starts from the local level and works its way up. But, it also starts with our applying pressure when we put someone in office, as with presidential elections, for them to do the right thing. FDR was not a liberal when he got into office, but the ground swell of suffering and the pressure placed upon him to do something transformed who he was.
Anyway, I have been reading the disagreement and needed to say something somewhere, so I said it here. Gotta love my self-indulgent blog!