There are many theories, but no one is quite sure where the practice of throwing shoes over raised urban infrastructure started. Some suggest bullies take shoes from other kids and toss them over power and telephone lines; other think it could be a way of marking gang or drug-dealing territories. Or perhaps people just make and lose bad bets, paying the price with sore feet.

Source: Anti-Gravity Boots: London Shoe Artwork Defies Laws & Physics | Urbanist