On getting conned.

We feel better today. The bane of 2015 was people who ordered books and never completed the deal. We even managed to sell the same book twice- the second time, at a reduced price- to the same person without ever receiving a check and shipping it.

Turns out it's nothing new. Here's George Orwell in 1936:

"But apart from these there are two well-known types of pest by whom every second-hand bookshop is haunted. One is the decayed person smelling of old breadcrusts who comes every day, sometimes several times a day, and tries to sell you worthless books. The other is the person who orders large quantities of books for which he has not the smallest intention of paying. In our shop we sold nothing on credit, but we would put books aside, or order them if necessary, for people who arranged to fetch them away later. Scarcely half the people who ordered books from us ever came back. It used to puzzle me at first. What made them do it? They would come in and demand some rare and expensive book, would make us promise over and over again to keep it for them, and then would vanish never to return..."

http://orwell.ru/library/articles/bookshop/english/e_shop