I've not had that happen although I've only been asked a couple of times and during the time I'm making the changes in the auction I'm in contact with the buyer. I feel bad for the person who asked you to BIN. But then again...you snooze, you lose...after all...it's eBay!
I had someone ask me to do a BIN. I said fine, added it, emailed the buyer, and never heard from him again. So after a day I took the BIN off the auction. You never know what people are going to do, I guess.