Burner phones of stuff of a movie director's dreams. An untraceable approach to instant communication for international sting operations, bank heists and car chases. Pre-paid, no one knows the user as he or she races past the convenient manhole, snaps the phone in half and throws it into the depths of the earth, speeding off into the sunset. That is, apart from in Japan, there they mainly don't exist, and where they do, you need your passport registered to it first. So much for anonymity.
And this is where it gets interesting. In its day the prepaid market in Japan was growing rapidly until its reputation became entangled with organised crime. Despite the ECB (a European business association) pointing out that the usage by the underworld of this convenient form of communication (for the younger and those with zero credit rating) had been traced to less than 0.1% of illegal activity on a usage basis, the government decided it was time to act. And pre-paid phones were effectively banned in the early 2000's.
However, they still exist. Just. Foreigners flying into the country can pick them up at the airports. But, in a similar fashion, organised crime, funnily enough, still exists. So burner phones are largely a thing of the past here and the police are happy and the consumer's memory too short to remember them. And seventeen year olds who are not legally allowed to contract for a phone (or anything) still need to rely on a parent or older friend. Will be interesting to see how the lowering of the voting age from 20 to 18 last year is going to change things. Go out and vote; and maybe you'll get your phones back. It's your elders who voted them out.