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...the next pick to the people who saw you pick the "winner". Now half of those people see one team, the other half see you pick the other team, and whoever saw you pick the winner thinks you've got a 100% accuracy rate over two games. You could do that for a while and then offer to sell your pick for the Superbowl. Starting with a big enough group in the beginning, this might be really lucrative.
But is it legal?
Search YouTube for "derren brown horse racing system" and learn from someone who did it. I believe it includes a discussion of the legality of it, at least in the UK.
Of course he did. This idea can up when we were discussing street psychics (magicians, hypnotists) like him and David Blaine.