I've been trading daily for 15 years...
And even in a highly regulated environment like the NYSE...
You are constantly cheated in various different ways...
But it's more like chiseled for pennies that add up over time.

Since MtGox has a monopoly on BTC pricing and is completely unregulated...
They are systematically manipulating the market to max their take...
Profits from these 20% moves like today dwarf that dinky 0.5% fee...
Because they probably do a LOT of large, private deals off-the-books.

Just about everything I ever read about MtGox negative...
I'm sure the truth is worse than anyone can imagine.

Ironically, BTC has a single point of failure = career criminals MtGox...
If BTC is soon co-opted and made irrelevant by Paypal or a Bank...
It will be because MtGox kept this market in this Stone Age...
And prevented BTC from becoming a stable currency.

Cue the Apologists from Gox who have infiltrated this place... 3-2-1.