Duh! They're all scammers! Craigslist is a wonderful thing, but has rapidly become the scammer's medium of choice. I won't use it for the same reason I won't eBay - it's just not worth it to me. I don't feel like trying to judge character to save a few extra dollars. I've only sold a couple of things via eBay, and those times I had my friend Rob (an eBay nut) sell 'em for me - and the last time we did so we dealt with a jerk in CA who was trying to rip off my old iPod. Screw that.
If you're looking for a used sofa within driving distance, Craigslist is awesome. If you want a laptop, go to the vendor directly. If you want to save a few dollars, there's a web store called Amazon that I hear is pretty good.