Bunnahabhain I didn't process your question properly as I was on the Diebold train of thought! Your absolutely spot on, "hanging chads" is not the answer to the question you are asking.

I have no idea why pen and paper is not the chosen method Nationwide.
It is still used where I live here in Northern Maine, but this is a very Rural area with about 400 Residents and we all use our Pens and 'X' marks the choice on the Paper Ballot.

I can think of reasons why the voting system changed but they are only my thoughts on the subject therefore not based on fact.
Hopefully someone in the 'know' will offer an answer. I am obviously not that one!:>)
Best Wishes
Jude