Recently I attended a food-tasting event. In addition to sampling a variety of entries of the type being highlighted, the paying attendees were handed a paper ballot and instructed to vote for their favorite food sample. The organizers assigned each presenter a number so all we had to do was write the number on the ballot. As the first wave of tasters passed through the hall an announcer reminded us to vote, and also to write our name on the back of the ballot to enter for door prizes.
There was one major problem (as well as a couple minor ones) with this scenario: