That's not true because they have voter ID #'s that identify the voter (as seen in that previous post with the person thst voted 29 times).it apparently cannot be identified once in the system. definitely presents a problem.
an analogy I've heard is that we all know there's an egg in a cake but once it's incorporated you cannot find the egg.
it's also the problem with fraudulent registrations - if a vote is cast on a fraudulent registration or even if one is cast using a valid registration but cast by someone other than the registrant it is in the system