I had read Dan Bricklin's illuminating essay "The Cornucopia of the Commons" (key quote: "increasing the value of the database by adding more information is a natural by-product of using the tool for your own benefit"), but just discovered another one by David Bollier with the same title that is equally interesting. It draws parallels between the gift economies of the NYC community gardens that sprang up in abandoned lots in recent decades, of the hacker and science communities, and of blood donation. The self-interest angle is in there as well - here's a quote from the conclusion:

It is a mistake, also, to regard the gift economy simply as a high-minded preserve for altruism. It is, rather, a different way of pursuing self-interest. In a gift economy, one’s “self-interest” has a much broader, more humanistic feel than the utilitarian rationalism of economic theory.

[Seb's Open Research]