From the Trenches of Electronic Voting
Avi Rubin, an expert on electronic voting systems, worked as a judge in two elections in 2004, and he worked the chaotic Maryland primary election yesterday. His blog article about a day spent with Diebold voting machines gives impressions from the trenches of electronic voting. From the article: "The least pleasant part of the day was a nagging concern that something would go terribly wrong, and that we would have no way to recover. I believe that fully electronic systems, such as the precinct we had today, are too fragile. The smallest thing can lead to a disaster... I can't imagine basing the success of an election on something so fragile as these terrible, buggy machines... As far as I'm concerned, the 'tamper tape' does very little in the way of actual security... I hope that we got it right in my precinct, but I know that there is no way to know for sure. We cannot do recounts."
Yes, in theory you could contact everyone. Why didn't they just do that in Florida? (that's mean, I'm sorry)
Without a physcial paper trail, which I hope could be verified by the voter, recounts would take a VERY long time.
Furthermore, even if you could reliably contact each person, who is to say they are going to tell you the truth? They may have voted for X, but once questioned can't remember and just say Y. That is why you have one chance to vote, no take-backs.
Finally, without a physcial, voter-verified paper trail; the software could invalidate an entire election. With the software controlling every part of the voting system, even the backup (if it is only electronic) one bug and the whole vote must be done over. With a user-verified, paper copy; even if the software screws up, it is the users fault for not checking the paper backup, and their vote is their vote.
Final note, really this time. If you give someone a reasonably simple voting mechanism, and they screw it up, that's ok. If you give them a reasonably simple, electronic voting mechanism, and it screws up, there goes the democracy.