I'd volunteer in the car example because I don't want a corvette. ::g::

Seriously, though, this is basically pretty similar to the classic prisoner's dilemma (http://plato.stanford.edu/entries/prisoner-dilemma/). The choices that get made depend on who stands to benefit, and on the relationship of the people involved. Of course, people aren't always rational in real life. But in fiction, I would expect the decisions to reflect the characters.

In other words, John Sheppard would totally volunteer. Rodney McKay would figure out a different, briliant solution to the problem. ::g::