All I ever see on the CL in my area is people trying to sell Rebel bodies and kit lenses for about twice what they're worth. Looking through earlier today, saw a used 18-55 listed for $150, when you can buy them brand new for cheaper than that.
Most of the time yes I agree. But once in a long while you'll find a great deal. I recently found a 24-70L for $700 and a 17-40L+1D3 for $900. Neither were stolen and I'm pretty sure of it. You got to be lucky and have cash on hand.