Following a link from Gary Carson’s blog took me to this article which states - probably correctly - that ordinary people are very prone to taking even-money bets, but hesitate to accept 5:1 odds on something. The example they use is someone who is very certain that a democrat will win the presidential election this coming fall, but still won’t accept 100:1 odds on it. Or even 5:1. It briefly explores some different ideas as to why people feel that way.

I just figured I’d add this: If you want to bet against other people, and they only want to bet even money, bet them over/under.

Over/under means that you (or they) offer an even-money bet on a certain figure. For instance, maybe they’re sure that a democrat will win the election, and you can offer them over/under on 57% popular vote. If they think a democrat will win with a larger margin, they can take the over, otherwise the under. It’s a pretty neat way of betting.