A recent wired article tried to ask whether you could disappear in the digital age and if anyone could find you. Wired did a test with writer Evan Ratliff as he tried to vanish. He didn’t tell anyone where he was going and tried to disappear as anonymous as possible. This meant using prepaid credit cards. To disappear he also changed his disguise on a daily basis.
In fact during his time of disappearance, he socially engineered his way across the united states (and used our travel systems of railway and buses) without any form of government issued identification.
During this time there was also a $5,000 reward if anyone could find him. He spent his time feeling paranoid though I doubt anyone really would have spotted him, since probably this story was smaller than he thought. Still the entire story sheds insight into ways he was able to travel without any form of identification.
The full story can be found at Wired