Shoe cleaners, Delhi
You may just laugh on the tip when you read it in your guide books, that be careful with some of the shoe-cleaners, those nasty ones, who have not got big and heavy stuffs to carry (so that they can run fast), because they can put sh*t on your shoe that they want to clean for double-triple price. We also laughed on it.
After like an hour in Delhi, at the Connaught Place one of us experienced it, which since then we call "The Palika Bazaar Incident". :|
It was a horrible thing that in the last couple of days we had to watch our shoes instead of looking around.
Another popular scam in Delhi is when someone throws garbage or feces on your shoes while you're not looking, and then graciously offers to clean your shoes for a small fee. I witnessed this happen to a couple I was speaking with and advised them just to walk away and not encourage this behavior.