Well, it's great that pre paid can be tracked. How about the first time they are used it is as detonators to kill a bunch of people crossing that bridge on Labor Day? So what if we could track them all...the people are already DEAD!
It should only take one phone though right? What are the others for?
Well, we need to outlaw and confiscate every digital clock circuit. Because that is the only functionality left available. Think about it. Is that really viable?