Philanthropists for years have used the "prize model" to spark societal innovations--from space (the X Prize) to the environment (Goldman Prize). The idea is to create a mercenary incentive to create broader social good.

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Now a billionaire doctor has come up with what could arguably be the most unusual philanthropic prize of all. It is called the Michelson Prize, named after billionaire inventor Gary Michelson. The cause: pet contraception.

Specifically, he is offering $25 million to anyone who can come up with a feasible dog and cat contraceptive. According to a post by Deb Wood on OregonLive.com, billionaire Gary Michelson--who earned his fortune from orthopedic devices--also is offering grants totaling $50 million for research in the area.

Before you start in with the doggie jokes, it should be noted that Michelson is serious about the issue, which goes by the name of "non-surgical sterilization" research. He formed the nonprofit Found Animals Foundation in 2005 to use scientific and innovative thinking as part of the solution to pet overpopulation problems.