"Social Impact Bonds" - A New Way to Support Juvenile Justice Programs that Work?

As part of his proposed budget, President Obama will be proposing that $100 million be spent on "social impact bonds."  The idea is that private private partners work with the government to invest in programs designed to address specific social problems. If the programs work, the federal government pays them back -- sometimes with a bonus -- but if the programs don't work, the government pays nothing. 
According to an article on this in The New York Times (log-in required), the president's budget is setting aside the $100 million for seven pilot programs in different areas -- and one area is juvenile justice. What will programs in that area target? We don't know yet, but John Kelly, in his weekly Youth Today column, speculates on what "social impact bonds" might look like in juvenile justice.

What do you think?  Is this a good idea? If so, what would you fund this way? 

Photo: Blip.