The news media seems to be telling double-voters to go ahead because they will not be caught. I don't think it would be that difficult to determine whether people have voted twice by using the voter rolls. Everywhere I have lived I was on the voter rolls as a person with my name living at a certain address... Now how likely is it that two people with the same name and birth date and live at the same address? And, it isn't too late to prosecute those who voted twice in 2000 - some states are doing it and the penalty is tough for those convicted.
Who is prosecuting?
Dual state registereds might also be committing crimes by evading the IRS if they failed to file state tax returns.
The IRS would be interested in dual state residents not filing state tax returns.
If a person is registered to vote in a state, that means that they are a resident of that state and as such, need to pay the state taxes of a resident, as necessitated by law.