Also, whether it is actually possible with an electronic system or not: It is really important that the (below) average voter actually understands that it is impossible for anyone to figure out who they voted for.
Paper ballots are handled by multiple people, not just the voter. Even if you manage to filter out all the volunteers, getting access to the actual ballots might prove difficult, as they're handled quite publicly.
Filtering the volunteers should be quite easy as they will be the only people who have prints on more than one ballot. Depending on what happens to ballots after one could grab them once they are no longer under heavy public scrutiny.
