they typically don’t. this seems to be why many of the users prefer it. i think i generally agree with them—it leads to a different style of interaction. i haven’t figured out yet how to elequently describe it, but the interactions and experience is entirely different from a for-profit site. it feels “more pure” or something (though i do recognize why description is inadequate.)

when “how do we monetize this?” becomes the driving force of a social thing, the experience changes in very real ways.

in general they're either labors of love or they run on a donation basis. it's a really good question.

They don't.