As Mike Arrington notes in his post at TechCrunch, this shouldn’t be that surprising really. Craigslist is simply a mirror that reflects human behaviour at its best and possibly at its worst. Why does that have anything to do with the site itself? If someone arranges for a hitman to take out their spouse, and the medium of communication happens to be a newspaper ad, should the newspaper be liable? Hardly. If I call someone and arrange a bank robbery, is the phone company to blame for that?
Craigslist is simply an instrument. Obviously, if it publishes an ad that it knows to be fake or illegal — like the listings on eBay for human kidneys and so on — then it is potentially at fault. But it has no way of knowing whether Robert Salisbury of Jacksonville actually wants to give away all of his possessions, nor should it be expected to.