I've had two buyers claim they paid by PP and I had no record of either one, in PP or in bidStart. When I replied that they need to send me some transaction verification, I never hear from them. I neg those immediately and block them.
Lately I've had two distressing buyer behaviors happen, nothing serious but bothersome. I've had buyers purchase large numbers of items (over 50 in one case) and they either do not leave any feedback, or only leave feedback for one item. I'm not sure if they know how easy it is here to leave feedback for large numbers of items from one seller; it is a pain at the other place, for example, where you have to do them one at a time. Maybe some education for new members is needed?
The other trend is for buyers with decent feedback fail to pay or communicate, typically for a single item and typically auction wins. I'm not talking about the guy with zero feedback that made the 10c bid and won; I'm talking about someone who outbid other bidders and never paid, despite two invoices and over one month of no communication. Perfect feedback up to then, and feedback AFTER they bought my item. Are they not getting notices they won?