Interesting paired bet. I guess it's not quite as good as a bond in the sense that a bunch of people you might not want to trust have your money for six months, plus your credit rating will record that you're an online gambler. But it's a very nice "risk-free" return all the same.
very valid points. I agree it's all personal preference, but some of the returns are, to me, too good to miss. I got a 1% return for a day (okay more like 4 days once you take their processing times into account) today on the Japan vs Thailand football game. (Bought at 1.0833, sold at 1.07) and it works out at something stupid like a 500% AER risk-free. Granted, people can't use their whole stache on it, there's maximum bets etc. Also have to take into account hidden costs of the risk of being drawn into actual gambling if you spend a lot of time on the sites.
But it's still an option I guess!