One other good reason why e-voting may be a bad idea is that it opens the door to the powerful pressuring others to vote in a particular way. The secret ballot is important; if voting in public is possible, and it's possible to have some verifiable way of saying that a particular person voted a particular way, that can lead to abuses where, for example, employers force their employees to vote at work where their screens are being watched.
Good e-voting systems would allow you to change your vote as many times as you want before the deadline. This makes pressuring/bribing ineffective, as you are able to change your vote afterwards.