This is not a "subtle problem" at all. Voting booths have curtains, and campaigners are constrained to stay away from polling places specifically so that you can cast an anonymous vote free from outside coercion or influences. With Internet voting, no one can tell what is going on whereever it is that you are voting from. Is someone pointing a gun at you? Is your boss watching you?

In Italy, they recently had to make it illegal to carry cell phones into the booths because people were being forced to use camera cell phones to "prove" that they voted the "right" away.

Voting should be done in polling places, using auditable ballots.