The wrong person alone with the machines for just a few minutes and another precinct is cooked. Yup.
Look, given untrustworthy poll workers? Of course.
Untrustworthy poll workers can do a whole lot more damage if the ballots are punch-cards than if they are paper ballots which voters mark with a pen. (See 2000, "dimpled chads".) Untrustworthy poll wokers can do a whole lot more damage if ballots are electronic, than if they are punch-cards. Essentially, the potential for poll worker fraud is magnified exponentially, the more sophisticated and "mass" technology that is used.
That is why I advocate paper ballots.
Nowhere did I say I wouldn't keep a better eye on poll workers if necessary. Of course I would. But "there could be dishonest poll workers!!" is not an argument against paper ballots per se. It is an argument against, first of all, trusting poll workers too much. It is also an argument against voting systems which leave no paper trail, and/or whcih render ballots too identical/interchangeable/computer-friendly, and/or on which all tallies are kept on computer and can be spoofed by the push of a button. In other words it is an argument against systems other than paper ballots.