You mean you lost your "on paper" value of thousands of bitcoins that you bought for $0.10? No one is going to have any less money then they had earlier that day. Unless you are counting the gains of stolen btc from a greedy hacker.
but just to be clear, the gains weren't from a greedy hacker. they were from completing a trade on an exchange where the counterparty happened to be a greedy hacker. if i make money selling fruit at a fruitstand for cash, the fact that the cash is stolen doesn't matter in any modern legal system that i'm aware of. again, that's true even in the united states, which adopts the relatively unusual legal rule that stolen
goods can be returned to their prior owners even after an innocent purchase.
that said, i may in the zeal of argument have overstated my point. i don't mean to be accusing mt. gox of 'theft', and i wouldn't want what i said before to be construed that way. i'm really just calling for transparency and accountability, and my point is that mt. gox does not seem to have justified the propriety of a 'rollback' given the information that it has released so far.
if we're just toying around (which, to be fair, is the approach i, more than almost anyone else, take toward the currently prominent block chain, having mined more than ten thousand coins cheaply early on and not having the desire or comfort to sell them yet - or perhaps ever), that's fine, and we can treat whatever mt. gox does today or tomorrow as a mere experiment. but if mt. gox intends to be treated as a prominent, serious currency exchanger providing honest customer service, it should at least consider holding the trade proceeds from yesterday in escrow while turning over the matter to arbitration or at least a third-party financial audit. instead, it has apparently decided to summarily announce a course of action that it intends to take on its own, even while admitting that it won't make certain customers (who may have legitimate complaints) happy.
to put that differently, if i were a serious bitcoin speculator or investor rather than (with respect to bitcoin) a technologist focused on the protocol and the systems issues, i would probably insist that my currency exchange acted more seriously than mt. gox is apparently, from its announcements, intending to act. its disposition in this matter is questionable. its first statement was a heavy-handed one that almost sounded as if it was trying to manipulate the price ('The bitcoin will be back to around 17.5$/BTC after we rollback all trades'). its later statements amount to announcements of its intent without an attempt at justification, ethical considerations, or propriety.
it may be easy for some to dismiss the claims of people who 'made a quick buck' by putting on fortunate trades yesterday. but the point of the argument i'm making is that it is
not that easy. the argument may not be persuasive, but at the very least people should think 'yes, he has a point' - and if so, that means that mt. gox's unilaterally announced course of action, canceling a large number of trades, is probably hasty.
i mean this as constructive criticism. i have nothing against mt. gox, even though as i've pointed out many times over the last several months, they have not earned my own personal trust.
