again, you are talking about a regulated forex market with a real arbitrage. Bitcoin is not...Bitcoin is full of unknown exchangers who are manipulating the price via bots as they want. I am referring to the biggest ones. There is a cartel of 5-6 big exchangers.
Now, tell me that OKcoin who "owns" 90% from the BTC market ...it's for real; no bots, no fake transactions, no fake volume.
http://bitcoincharts.com/charts/volumepie/If there are fake transactions and fake volumes that means there is HUGE price manipulation which is "somehow" illegal

But, again, there may well be price manipulation - but price similarity between exchanges is not evidence of it.
And no, I'm not talking about a (solely) regulated forex market - I'm talking about a global forex market where many exchanges (in particular) are licensed and regulated, and many OTC money-changers may well not be.
There is no difference between arbitrage in a regulated market and arbitrage in a non-regulated market. If the price at one location is lower than the price at another location - it is profitable to engage in arbitrage, regardless of volume (fake or otherwise), regardless of the licensed/unlicensed status of the exchange, regardless of the regulations in place.
I could create two shady exchanges, AlphaExchange and ExchangeBeta. Neither are licensed or regulated. I fake the volume. You see a price of $450 per 1 BTC on AlphaExchange and a price of $455 per 1 BTC on ExchangeBeta - you realise you can make money if you simultaneously buy on Alpha and sell on Beta. In doing this you create demand on Alpha (pushing the price up), and you create supply on Beta (pushing the price down) - the prices on the two exchanges move towards each other. Both exchanges remain unlicensed, unregulated, and are (since they're secretly controlled by me and I'm up to all kinds of naughtiness behind the scenes) a cartel of two exchanges.
Honestly, this is not the smoking gun you seem to think it is. No one in the real world will look at this and assume that there is a cartel - even if there is. People will assume that this is normal - even if price manipulation is occurring.