Sorry that was meant they are propping volume.
I think the concept behind this is to increase volatility and as such the frequency of trades. Once the trading volume has gone up to this levels it will take a while for it to come down, during which they will collect fees.
As for their reputation: It's not like we can catch them doing it, we can either believe their explanations or come up with something our own. Neither of which can be proved either way.
I've had my own theories, which I won't rehash. I've seen some very questionable pricing and volume action on Gox. An unregulated exchange certainly leaves the door wide open to the full range of shenanigans circa 1920 NYSE.