It's a matter of probabilities - if you think the chances of btc-e going down _during one week_ are less than 0.12%, then this is a good deal.

You have insurance on your car right? This is basically the same thing.

Also, you don't have to risk 250 BTC. As I said, I might consider paying proportionally so you can put 50 and I'll pay 0.06. For one week, that's 6.4% interest rate so it's actually quite a good offer.