He's really using money as a proxy for identity/reputation/culpability. If you have something at stake, you are less likely to act like a jackass. Craigslist's

He's really using money as a proxy for identity/reputation/culpability. If you have something at stake, you are less likely to act like a jackass. Craigslist's propensity for scamming (and positive frictionless interaction) is because of its anonymity more than its cost.