In many respects, the design process seeks to understand and manage the Law of Unintended Consequences. I found this interesting from the Financial Times:
"I ask if there are certain hotspots where pickpockets strike. Tourist spots, Freedman tells me, especially places such as Big Ben and the Eiffel Tower, where people’s attention is directed upwards and away from their belongings. He says that many pickpockets also operate near signs warning us to beware of pickpockets. The irony is that when people read the signs, they check their pockets or bag, thus alerting the lurking pickpocket to where their valuables are."