In my experience, if the machine beeps and spits your ballot out, which it will always do if you don't vote on some of the elections (and I never vote the stuff I don't know about, like school boards) then the poll worker will grab it and try to shove it back in. I don't think they are trying to invade your privacy, they just are trying to be helpful. But, in the end, they aren't respecting the secrecy of my ballot.