pay as you go requires no contract, and they do not verify your ID.
Yet. But wait. A year ago in my state some nutball made a bomb that was remotely activated by one of those throwaway phones. Killed a bomb squad tech and maimed a city police chief.
From the remains they were able to identify the phone down to where and when it was bought, and identified a suspect by store security video from that time. But they'll say, you know, it's for the common good that folks (that's what corpse-man calls them) should have to show papers to make a phone call. Any phone call. Technology exists to do that right now and just wait, some "patriot act" 3 or 4 will have that.
Since 2000 the federal government has hooked into almost all of the communications infrastructure in this country and much of the world. The telcos (most of them) gleefully hand over any records and information they want, in order to stay in business. Only one (QWest) in the US offered any resistance and I believe those days are done.