The key to take advantage of suckers of this kind (that only bet on 50/50 odds) is not to make them realize their mistake by changing the odds. This is precisely when they start to realize something is up. I've won two bets against friends in the past six months doing this (though in the first bet the friend would have probably done something at uneven odds).
On the other hand, I have another friend that makes lots of overconfident assertions and, when possible, I try to make even-odds bets with him, but he usually refuses with some excuse about why it wouldn't be appropriate to bet. Even when I tell him to take advantage of my ignorance. I'm unsure how to crack nuts like this.
(For those of you who find the idea of taking advantage of your friends offensive, this practice also raises the sanity waterline - both your own sanity and your friends. So long as the stakes aren't too high, I think it's a great practice)
Today's post, Futuristic Predictions as Consumable Goods was originally published on April 10, 2007. A summary (from the LW wiki):
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