From CSULA CS Wiki
I don't know whether or not this is apocryphal, but it's too good a story not to repeat. Jochen.Fromm, who has a nice Complex Adaptive Systems page, writes about
a funny story our professor has told us. The government in India long ago tried to prevent the spreading of a snake plague, so they offered a high reward for every snake caught. The result was that the people started to breed snakes in farms in order to make a lot of money.It's so simple isn't it. Offer money for snakes, and people will find ways to supply them.
I was recently told that a variant almost happened in Iraq. The US Army was considering offering a reward to people who brought in unexploded IEDs (improvised explosive devices), the roadside bombs used to attack US Army vehicles.