I have this eBay habit. I buy and sell (buying more than selling of course), and over the last several years I've had pretty good luck all around.
But not long ago I bought an old SF magazine from one of those dealers who has a long list of "rules" for buyers. If you win an auction and he hasn't heard from you in three days, he's going to turn you in as a deadbeat. And if you haven't paid in ten days, you're scum, and he's going to turn you in. And so on.
Well, I responded as soon as I got notification that I'd won. But I never heard from the dealer.
So I wrote him daily for about a week. Finally he responded and told me the amount of postage due. I paid him by PayPal as soon as I got his e-mail.
More time passed. A lot more. But today I got a magazine in the mail.
It's the wrong magazine.
So I e-mailed him immediately. Guess what? No response so far. Why am I not surprised?