As far as i understand it: They were not left up because people liked them so much, but because there was not enough funding to take them down. Or rather, no one would spend their own funds to make happen. So the babies are left hanging in limbo. (Sometimes the Kafka-esque bureaucracy here in Prague has its pluses.)

David ?erný has done some other great city-size installations: http://www.davidcerny.cz/startEN.html