One interesting point about this concept is that one of the limiting factors was likely that it was too complex to keep track of who had whose vote. Traditional

One interesting point about this concept is that one of the limiting factors was likely that it was too complex to keep track of who had whose vote. Traditionally, with paper and bureaucracy, it would have been a near impossible task to calculate that on the day of the vote, Carol has been delegated Bob's vote and Alice's and that neither have rescinded such delegation prior to the vote. The paper trail made it infeasible. However, now that we have computers to do most of the figuring, things can happen in near real-time thereby removing this constraint and making this (more) possible. Certainly there are many other side issues (authentication of Alice delegating her vote to Bob, did she do so under duress?, etc.) Very interesting idea though and, as you said, probably an old idea, but one that may have been scrapped due to these technical issues. Now that we can overcome them, seems worth revisiting.