most of this is wrong. the reality is that people do not transfer money onto the other exchanges.
why would you trust bitstamp when its ripples fbuddy?; ans: you shouldn't.
why would you trust btc-e when it is russian or polish?; ans, you shouldn't. site is in russian, bank is in poland etc etc, its ambiguity is good AND bad
SO, nobody trades from Gox to other exchanges unless they want to lose 5-7% buying power, they just don't do it. they HAVE to have a very good reason for performing this action, stocks LTC, other coins with a profit larger potential, safety.
They get in, get their stuff onto their private wallets and sit. OR they trade on Gox.
The buying pressure comes from Gox's ability to attract customers, A LOT OF THEM, more customers transfer money to them and buy bitcoin than ALL the other exchanges put together and doubled, possibly trippled.
Also dont trust Gox either
Remember kids, OTP, Two Factor authentication is there for your latex protection.