I love the idea!!! I even dream of the day that we can vote online. We could secure the "transaction" from fraud by requiring the use of a Smart Card
http://computer.howstuffworks.com/question332.htm. We are required to use the Smart Card as Federal Employees to login to the network. The card is our employee ID Card as well. This shouldn't cause any fear of a National ID card since you can get a card from a multiple government and private sector sources, possibly your employer. You could login from anywhere that had a Smart Card Reader and software.
http://www.athena-scs.com/product.asp?pid=1 not just limited to your home or office, but even ATMs or other point of sale devices. The only requirement that I see as a necessity is the ability to
KEEP YOUR VOTE PRIVATE!!!
The upside as I see it would be that voter turn-out would skyrocket.
The main downside would be that, for both this idea as well as the ATM voting machine, is exit polls. Without exit polls how do you gauge if the factuality of these processes? The other is that many would see it as a need to abolish the Electoral College system.