[vinylkey]

Seems difficult to do. You'd need to know the name and address of the voter, and be sure that that haven't voted yet, and won't try to vote after you.

I can see that happening maybe a few times, but it seems ineffective on a large scale.

[SilasX]

Most of that isn't true. When I lived in California, you simply asserted that your name was X, where X is someone on the list, and you got X's ballot. No need to know their address.

If they already voted? "Oops, I forgot."

If they haven't voted and come in later, so what? You're long gone.