If you are into Bitcoin for short term speculation and want to be able to react to the market quickly without having to sell them for a pre-determined amount it makes sense to leave them on the exchange.
Just saying.
Yes, but with a >10x of amount shown on the book is still far too much IMO, especially when gox has all sort of problems
I know I have coins at stamp that are not in the order book - I don't use Gox but why wouldn't people have done the same thing? Allegedly they had 500,000 accounts - ( inflated number probably) but if every account just left 1 coin there it would be most of that number.