When my youngest son (wrestler, not baseball player) was in high school, the local TV station held a on-line vote to decide which of 3 potential football match ups it would televise each week.
The first time our school was on the ballot, my son wrote a little routine that an instructor permitted him to load on all the machines in the computer lab so they would keep voting for our game over and over again all day and all night. We won, with more votes than our congressman had received in the previous election.
Smart kids at other schools caught on quickly. A few weeks later, we were again on the ballot. This time we lost even though we had about a hundred times as many votes as in our earlier victory. Eventually the grownups at the TV station implemented some controls and put a stop to the ballot box stuffing.