When the exchange is not regulated by the government, it will be regulated by their customers.
Push things too far and all their customers will take their money elsewhere.
But there isn t much choice for the "elsewhere", especially if all of them are abusing their position.
If "customer regulation" was enough, there would have been no need for government regulation.
One problem is that many of those exploits are nearly impossible to detect by looking at the trade logs. Their only effect is to make all ordinary clients less lucky. E.g., the ordinary trader who posts a sell order will have it filled by a buy order at his ask price; whereas, if the exchange were honest, there would have been a buy order at a higher price waiting for it.
Last May, the five largest Chinese exchanges, apparently scared by some government pressure, released a joint note pledging (among other things) to end leverage trading and put a fee on high-frequency robot trading. I read between the lines that they were caught doing some dirty tricks (which depend on fast-acting robots), and were scared enough to stop, or cut back on them.
I would even guess that those dirty tricks were responsible for the general downward price trend from February to April, as ordinary Chinese traders were disappointed with their "bad luck" and cashed out, one by one. Indeed, that "five-exchanges" note coincided with the end of the downward trend and a month of steady price.