When thinking about such things, you have to consider the laws of unintended consequences. If a specific ballot can be assigned to a specific person, then the secrecy of the ballot has been destroyed. One consequence of this destruction is that it actually aids some types of fraud, like vote-buying, because if you can know how a person voted, rather than just taking their word for it, someone whose vote is bought, will stay bought.
Personally, if someone ever offered me money to vote for a candidate, I'd readily take the money, then vote for the other guy.
very true but with computers i think your vote is numbered and recorded. they know who you voted for. Here in philly you (used to) get a number assigned and it was verbal but you knew the number and if you wanted to you could go back and verify how the old machine recorded the vote no one else got the number.