Tired of drivers speeding by in front of his house, Mike Wood of Ohio created life-size cardboard cutouts of his children and put them up in his front yard.
So far, Wood said it has worked. Motorists have slowed down, and some have even yelled at Wood for letting his children play so close to the street. [...]
His idea has already been posted on some law enforcement Web sites around the country. He's now selling the signs for $60.
Link - via Hemmy and Blue's News
As others have said, it's also a form of "crying wolf". For example, my neighbours' kids might be being abducted because they're screaming their heads off in the yard. But they do that all the time, so nobody pays any attention anymore. The same thing could easily happen with these signs.
Caltrops!