I was at the FLoC 2006 conference over the last ten days or so. While there I saw David Dill give an invited talk about electronic voting. I was struck by the analogy he drew to describe almost all current electronic systems.
When using an electronic system, it is as if one goes into a voting booth to find that one has to dictate one’s votes to a man behind a curtain who says he will fill out and deposit your vote in the ballot box, but that you will not see any of this happening.
No matter how much faith you might have in the implementors of the system to have implemented it correctly, and to have defended it against possible attacks (i.e., no matter how much faith you may have in the man behind the curtain), such a system fails to be transparent. And transparency is the great virtue of traditional paper systems: everyone gets to see the democratic algorithm in action at all of its stages, and to check that it is being performed correctly.