If you want a concise example of incentives gone awry, I believe there's a Terry Pratchett quote of the form "The king announced a bounty of one shilling per ra

If you want a concise example of incentives gone awry, I believe there's a Terry Pratchett quote of the form "The king announced a bounty of one shilling per rat tail. Within three days, the first rat farm opened." I'm sure someone can provide a more faithful quotation.