Exchanges decoupled price

[Dotto]

Im seeing the price is decoupled since 7-14 days at least, normally +20USD in bitstamp. From a somehow newbie point of view, I see it as a potential bad sign, reminds me somehow the MtGox decline, but Im not sure how to read it and I guess it could be related to the Chinese news.

Could you explain what´s happening and share some light about possible consecuences for the BTC economy?. Why the traders are not arbitraging it fast for profit?

[Wilhelm]

Not all exchanges have the same rules, fees or volume.
If an exchange is $50 higher but only has 0.23 bitcoin in the orderlist it doesn't actually count

If arbitrage isn't possible or not worth while then decoupling will happen to a certain extent.
Arbitrage can be hard or not worth while if fees or risk is high. Arbitrage will give you a double fee hit and a timeloss whilst moving inbetween exchanges.
At that point your money is in another exchange and you need to get it back to the other exchange (possibly through another exchanging method) again for a second run giving you more fees or timeloss.