Went to a "Battle of the Bands" contest. It was in a bar and the audience got to vote. Everyone was given cards numbered 1 point, 3 points and 5 points. Voting happened after each band played. We'd all gone to see a friend of a friend so the obvious strategy was to vote 5 for that band, and not vote for the others.
Turned out they did the voting differently here: they computed the average score rather than the total score. In a fixed audience, both average and total would produce the same ranking. But in this situation the audience changed. Battle of the bands is really "who has the most friends?" and people turn up only to see and vote for their friend.
So normally you'd vote 5 points for your band, and ignore all the others (who might be playing when you haven't even arrived yet or after you've left) and that would be equivalent to voting 0.
Using an average vote penalises you for this, though: your absence didn't count as a zero vote because you weren't in the total vote tally. To downvote a band that isn't your friends, you have to be physically present.
That seemed a neat way for the bar to make you stay and drink more beer.