Johan De Boer is a jeweler from the Dutch city Apeldoorn. I'd never heard of him either, until the 10th anniversary of his business...
Mr. De Boer had this great idea for a special anniversary stunt. He sent a promotional mailing to his 4000 customers and included a "diamond". 3800 of these were fake, the other 200 were in fact real gemstones. In the accompanying letter, he invited the customers to pay a visit to his shop and have him check whether their "diamond" was a genuine one.
Being surprised that only a few people showed up, he contacted several of his customers. It turned out most of them threw the letter away immediately. 165 real diamonds ended up in the trash that way.
"I've been enormously naive," says Mr. De Boer. "People don't trust it anymore if they receive something like that by mail."