I have recently come across a situation where a buyer pretends to be having problems setting up a paypal account, or other paying problems. She strings you along asking you to be patient and thanking you for being understanding, reassuring you that everything is in order.
This person is sndrbasile41k (I am not sure if I am allowed to name here) is very convincing and, if you let them, will continue to keep regular contact with you until the 60 day time limit expires and you are no longer able to do anything about it. Once this has happened, you are unable to leave negative feedback or report them via ebay, but you will have been charged the ebay commision even though you have not received payment.
She is based in Florida, USA and has a low feedback score and I suggest all ebayers be on their guard and report non-payment to ebay as soon as the 28 days have passed regardless of how nice the seller may sound.