Not a horror story - just one of those funny deals:
A dad comes in with his 12 yr old kid, buys him a nice bike and everyone is happy. The next day they come back all upset because the bike has no brakes, they kid can't stop it at all. I checked it out and sure enough, absolutely no stopping power, even though they worked fine mechanically. After a little conversation, I discover that the kid was so proud of his new bike that he wanted to shine it up, so he got his dad's spray bottle of Armorall and went over the bike with it - including the tires and rims. He did a good job.