Great points. The key as a SELLER, is to protect yourself. Take tons of pictures before you ship of item condition and any damage, ONLY accept PayPal or Money Orders, KEEP THE SHIPPING RECEIPT, and pay the extra for a signature confirmation.
If you use PayPal, they have a "multi-order shipping" system, where you can pay, and print shipping labels right there from your paypal. Then, PayPal cannot say you didn't ever ship the item. EVERY item shipped with PayPal automatically gets Delivery Confirmation, but make sure you check the box for signature confirmation.
As a BUYER, NEVER pay as a Gift. Just add 3% to your transaction and cover the fees. Also, request TONS of pictures. If the seller only has one or two pictures, move on. If they can't be bothered to take as many pictures as you want, they can't be bothered to sell their item.