I agree... This is not the best practice around.
What I would do as a seller, to avoid similar situation is not to give Paypal account (assuming this is the method of payment) to many people at the same time. Just make sure I have 1 firm buyer (usually the first person to say I will take it). Confirm it again (asking for details such as location, etc.) and then after second PM, I will give my PP account. This is to avoid double payment/etc.