I agree with Accordion, Craigslist has made a significant dent.

As a seller I don't have to pack or ship anything which is a major hassle. I also don't have to worry about anything getting damaged in transit. Last year I sold a pair of shifters on Ebay. When the buyer received them, the right shifter wasn't working. It was packed well. I have no idea what happened to it. All I know is that it was ordeal for both myself and the buyer. I refunded the money and got the shifters back but of course I could only sell the left one after that point.

With craiglist, there are no fees and the buyer gets to examine whatever it is your selling on the spot. Once it leaves the premises your obligation as a seller is fulfilled though I usually tell people if they have a problem I'll take it back as long as it's only been a week or so.

Finally, posting an add on craigslist is pretty quick and the standards are low. It's easy to create listings that stand out just by adding links to good pictures.