[jpollock]

Anonymity keeps the government from locking you up if you vote the wrong way. Non-demonstrable keeps you from selling your vote to your boss.

That is why you typically show id, get a ballot and there is no relationship between the two.

[VladVladikoff]

I could still sell my vote to my boss in the typical system.

And we could use cryptography to vote anonymously after authentication online.

[indecisive_user]

In the current system how do you sell your vote?

You go into the voting booth alone.

[drchaos]

"I give you $50 if you vote for me, you'll get it when I win the ballot"

If someone is willing to sell their vote in the first place, they have zero incentive to vote for another candidate. They only have to trust the buyer to follow up on his promise (which is required in any other scenario also).