Which naturally raises the following question: why are we following [China]?
Arbitrage trading seems to be a good explanation. If the price drops significantly at Huobi but not at Bitstamp, for example, someone promptly buys BTC at Huobi and sells them at Bitstamp, until the prices even out.
To play that game well, one needs quick reflexes (= robots) and substantial accounts of BTC and national currencies at both exchanges. It does not matter whether your profits end up in China or in Bulgaria, you can transfer them later with bitcoins or any other method.
Because of arbitrage trading, market prices are usually more or less the same in all markets, with due offsets because of trading fees or other exchange-specific factors (such as transportation, storage and customs costs in the case of material goods).
That's why that 130 USD premium at Mt.GOX is so worrying. Arbitrage traders are obviously not operating there. And who could be buying the overpriced coins that people are selling there?
PS. Arbitrage trading is considered good because it makes one large market out of the separate exchanges, so prices tend to be more stable and the spreads between buy and sell are usually lower.
