Because an individual act of free-riding may be part of a pattern of behavior that is, on net, both efficient and fair, for certain types of cases it may be that we want to ask, not: "Has this person acted correctly in this case?" but rather "Is this person, in general, a sufficiently helpful sort?"
This reflects my own current position. Contrary to the usual model used in economics, people are somewhat good. We should try to quantify this, develop social institutions that increase the strength of this effect, and engineer situations where it can express itself.
I have in the past favored classical economic solutions. However this is more powerful, I think.