People are not very good at realizing that "sunk costs," i.e. investments they have already made should be disregarded when they are deciding whether to make future investments.
This is a pervasive fallacy, and informs such otherwise difficult to explain phenomena as the persistent popularity of Farmville, the reason that people are more likely to hold on to losing investments, and "...keep clothes in their closet that they’ve never worn" (Investopedia).
It's one of those irrational quirks of the human animal which calls into question many economic models that are based on rational decision making (but that is another discussion entirely).
I wonder why we don't use some kind of framing though, with regard to the upcoming midterm elections which frames the decision as to whether to vote for congress as a sunk cost, for example something along the lines of the following:
You got out to vote for Obama in 2008. You voted again in 2012. Don't throw those votes away. Vote in the 2014 midterms.That's it. A very short diary.