That's true, although in the event of a crash, the value of your coins would be protected, because the MtGox 24 hour average would be consistently higher than the last trade price. Quite frankly, I don't know why anybody is spending at this point, when BTC value is increasing by $30 a day. I'd wait until the price stabilizes for a few days, at which point the SR/MtGox average would catch up the last trade price.