The problem with individually tracked votes is that I can then give my stub to my union boss (or to Karl Rove) and get my $10 for making the right votes.
I agree that could be a problem, so that idea could be scrapped.
The reason for the ballot-stub was and idea for "voter disenfranchisment" worries. It was discussed after the Florida and some others states (I think places in PA?) where discarded ballots were found in trash bags or some garage or warehouse of something. Memory is failing. But, this was an idea that would assure honest voters what happened to their vote: that is counted and how. NOT for other purposes like being redeemed for cigaretts or walking-around money for votes from party thugs kind of thing...