I once heard

about a beer brewer who walked into a bar with beer and handed out mugs of good beer to everyone. On every mug of beer was a label with the recipe. In his hand he held a sign: “Free beer.”
[...]
Some beer drinkers, now drunk, decided that the brewer had scammed them into thinking they were getting free beer. They called him names, said his first sign was BS and decided to use the recipe and start a brewery anyway. The brewer, advised that his first sign wasn’t BS tried to deter them from making that mistake.