I was just thinking about the following quote from a Robert A. Heinlein book:
"I do not understand objections to `cruel and unusual' punishment. While a judge should be benevolent in purpose, his awards should cause the criminal to suffer, else there is no punishment -- and pain is the basic mechanism built into us by millions of years of evolution which safeguards us by warning when something threatens our survival. Why should society refuse to use such a highly perfected survival mechanism? ... As for `unusual,' punishment must be unusual or it serves no purpose."
Robert A. Heinlein - Starship Troopers