I've had enough flakers and hagglers that I now post warnings in all ads:

1 - I refuse to hold anything (first person to show up with cash takes it)

2 - no haggling on the spot; I'll turn you down on principle

It's a fucking hassle. I buy a new macbook every 12-18 months and craigslist the old one (and the same with phones). I take good care of my hardware and carefully point out any scratches or nicks in the craigslist listing. People still try to knock you down 10% or 20% when they come.