Hear hear - Russell posts about the dangers of relying on technology; this time, on how using location-based services for locating children doesn't really solve any problem. The cynic in me wants to shout "stop mining paedo-hysteria for your own profit" at some of these companies, but I usually manage to restrain myself.
The first time an implementation of one of these systems fails, the whole system is worthless: in this case, the first time such a tracking device is worked around (by an abductor turning off a childs phone; by removing the RFID chip; whatever), the system fails to provide it's intended purpose: a sense of security for parents. (I don't think many people believe that LBS in phones acts as more of an effective deterrent to abductors when compared to, say, the law).
Much the same argument can be applied to ID cards: the first time one is forged or supplied fraudulently, the ID card becomes useless as a definitive means of truthfully identifying someone.
So why do we see such schemes? Because people really really want them to work; we really wish that 21st century magic could provide us with the answer, much as medieval alchemists devoted their entire lives to wishful thinking in pursuit of the philosophers stone. And because we really really want these solutions, we put on blinkers and pretend that technology has the answers. I see the same tendency in digital rights management...