A system which allows voters to audit his vote in the final result via a unique ID has been suggested. The arguments against seem centered around the secrecy issue and coercion.
For example, a boss wanting his employees to vote for his candidate, and coercing them to provide their unique id so he can verify.
The system would also enable vote buyers demand the unique id in exchange for money.
I don't doubt these could happen, but either would be a serious crime. How would that be different from someone demanding the login for my bank account?
These crimes would be difficult to pull off today with whistlblower methods available.
I think we really need a more reliable means to audit the voting system, especially since more folks will be demanding mail in ballots.
The current methods allow us no means to verify that our vote has been properly tallied in the final result. The ability to locate one's private id and audit one's selections in the final database would close that gap.