I haven't had any problems with Craig's List .. yet.
I've sold and bought a ton of stuff (cars, audio equipment, speakers, laptops, etc.) and knock on wood, I haven't got screwed. Like any private sale, you have to go the extra mile in checking the product you're buying, check their bona-fides to make sure they are who they say they are and deal in cash (make sure it's not funny money), whenever possible, if you're a seller.
For big-ticket items, like a car, insist on a bankers check and cash it at your local bank (ask a bank officer to double-check the validity of it before leaving) before heading over to the local notary to hand over the title. The same goes if you're a buyer. Verify his/her home address and make note of any promises made on the condition of the car/motorcycle in front of witnesses at the notary's office. Even better write up the terms of the deal and have that notarized too. For a mere $15/$20 bucks it's a bargain for the peace of mind.
If none of those terms are met, just walk away from the deal. You're probably dealing with a shyster.