When I was backpacking around Thailand a couple of years ago, there was a persistent rumor (often mistaken for fact) that Chang Beer and its competitor, Singha, contained formaldehyde. Apparently, that’s why they tasted so good, and also why we felt so awful the next day (right, because the fact that we had 12 of them had nothing to do with it.)
According to one of the locals, the government took the formaldehyde out of the beer, only to be met with outrage from its loyal drinkers because it just didn’t taste the same without that toxic preservation agent in it. After an instance of gut rot that I blamed on the formaldehyde, I decided to stay away from the Thai beer.
Turns out that’s all a load of hooey — there’s no formaldehyde in the beer, so I needn’t have avoided it so fervently. Other beer myths that you might have heard while traveling? That Guinness tastes better in Ireland (I still believe it does, if only for the atmosphere) and that Corona contains Mexican urine (apparently, this one was started by Heineken.)