There’s a new category of scams making the rounds (well, it was new to me): hostile messages supposedly from an eBay buyer saying things like “I want my money back because I did not received (sic) my item until now. I will report you to eBay as fraud if you will not respond.”
A major clue is that the item mentioned is nothing you have ever heard of, but I have to admit, the messages look very authentic, right down to the “marketplace safety tip” they include about not responding to e-mails! Of course, they aren’t real. If you get one, forward it (without changing the header or adding any comment) to firstname.lastname@example.org, where the fetchingly named eBay SafeHarbor Investigations Team will take over.