Interesting thought. Bitcoin circulates, and you have to wonder how much of it has passed through a fraudulent transaction -- at any time in the past. Someday when it becomes straightforward to walk the entire life of bitcoin backwards, there may be people who want their bitcoin back...because it's stolen property.

If A has a TV, B steals the TV and sells it to C, who sells it to D...then the TV is still returned to A, and D is out of luck.