[Variance]

Indeed. No one should be pitied for losing money in the stock market. If you know what you're doing, you'll know that there's risk involved; if you don't know what you're doing, you shouldn't be picking stocks in the first place.

People who lose out by being on the selling-too-low side of arbitrage have nothing to complain about. If you had a stop-loss order, you cede your position to the possibility of being sold too low. Moral being that like you said, if you're investing in something that might warrant a stop-loss order, you should be sophisticated enough to use something better instead.