99
...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?
What law would it be breaking?
Not really, If you started this at the beginning of the regular NFL season and included the playoffs in the run up to the super bowl, you would need to start with 1,048,576 emails to have one person see you pick every game prior to the super bowl. And this is only if you send an email for one game each round.
If you started and sent an email to every person who watch the super bowl last year (~84 million) you would only have about 80 people left at the end and you would have sent close to a billion emails to do it.
And then you don't even know if they bet.
Not sure about USA law, but in Australia we would call that “obtaining financial advantage by deception”. Otherwise known as “fraud”.
Any intentional deception for financial gain would be considered fraud in the U.K. at least.