Filming yourself could easily be prohibited. In France, I'm pretty sure that the voting officer wouldn't let me put my ballot if I was filming myself doing it.

Canceling mailing or e-voting ballots when voting in person can be countered by requiring that the person hand over his ID card for the vote duration.

The idea that a vote might have been bought is a dangerous one. It's dangerous even if votes buying are not proven. I'm still not convinced about e-voting for this reason. There should be absolutely no doubt on the sincerity of a vote.