Ed Felten at Freedom to Tinker has several brief, but meaty, posts this week on the erosion of a pillar of Western democracy: The secret ballot. The secret ballot offers two forms of protection: Because nobody can look over your shoulder to see how you voted, it's hard to coerce your vote. And, because you can't prove to anybody how you voted, you can't sell your vote. But technology and social trends are making the secret ballot harder to preserve. Phonecams pose a big problem.

You probably carry into the voting booth a silent camera, built into a mobile phone, that can transmit photos around the world within seconds. Many phones can shoot movies, making it even easier to document your vote. Here is an example shot in 2004.

Could such a video be faked? Probably. But if your employer or union boss threatens your job unless you deliver a video of yourself voting "correctly," will you bet your job that your fake video won't be detected? I doubt it.

This kind of video recording subverts the purpose of the voting booth. The booth is designed to ensure the secret ballot by protecting voters from being observed while voting. Now a voter can exploit the privacy of the voting booth to create evidence of his vote.

Felten describes a scenario where technology makes it easier to coerce voters without actually doing anything. And he explains why absentee ballots and voting-by-mail are extremely insecure..

Felten, a professor of computer science and public affairs at Princeton University, has been integral in disclosing flaws in electronic voting technology.