Potlatch: the Gift Economy. Needs some exploring.
Was just thinking about an interesting property of gift economies, such as Burning Man or (usually) the web: you pay to provide, not to consume. Consumption in a gift economy is free (ok, you pay a flat fee, like your ticket to Burning Man or your Internet access… but those things aren’t required). You can consume all you want, but if you want to provide something, that costs extra. And the more you provide, the more it costs you.