If it locates one criminal like "the “Ipswich Ripper” (a notorious serial killer) and the Neo-Nazi “nail bomber.” that the London police talk about their system doing, it might be worth the effort.

It might also identify the next round of violent protesters who decide that it's a good weekend to break windows, burn cars and stores and generally have a good time downtown.  

Or identify the one who stabs the next homeless person.