So there are only
BTC1.8k new BTC mined daily. Volume wise we got about:
BTC4k @ Bitfinex USD/BTC
BTC4k @ Btc-e USD/BTC
BTC3k @ Stamp USD/BTC
BTC3k @ Coinbase USD/BTC
BTC3k @ Kraken EUR/BTC
BTC1.8k daily Gemini auction
BTC1k @ LocalBTC USD/BTC
or about
BTC20k/day volume from somewhat believable sources
+
BTC21MM CNY/BTC
and that's with a stable price in last 3months. Where is the volume coming from?

can't be same people selling to themselves just to pay exchange fees
I think it is one thing only: fractional-reserve
https://bitcointalk.org/index.php?topic=945881.0Read that thread and most of your questions will be answered. At first I would not believe that was happening but it is.
But that's exactly why Finex implemented the the multisig with BitGo for easy auditing.. right? RIGHT??

I personally would like to have an answer for that but I don't: But I definitely quote the following
Q: I dont believe you, I dont understand the problem and I dont really mind. Are you just another conspiracy theorist?
A: Were not conspiracy theorist and whether or not you dont get our point its in your best interest not to store your BTC in any third party exchanges for too long.
Do you want to be the next Mintpal, Mt.Gox, Bitstamp etc. sad customer?
So, even more if you think we said a bunch of bullshits just bear in mind our golden rule
DO NOT HOLD YOUR BTC ON THIRD PARTY EXCHANGES BE YOUR OWN BANK