Because as I just said above its nothing to do with how big or small your walls are.
1) If you look at bid/ask support to base your trade decisions on quit trading right now, yesterday was a perfect example of this. The Finex books have been stuffed with big bids above $270 for a week or so. All of a sudden thousands of btc in bids gets pulled and the price dumps. Happens all the time.
2) OKcoin only shows 5% of its books if it showed it all you would see very large walls.
3) Yes volume and the fact its the market leading exchange, most the time all the other exchanges are being dragged around by China, it's been this way for a long time.
Note, a large majority of western traders also trade on chinese exchanges due to their low fees, higher liquidity and better order options.
I didn't trade on Gox (well, not since 2011) but I followed their BTC/USD exclusively until it became obvious something was badly wrong. It was around then I realised that BTC/CNY volume was higher than BTC/USD, and I started following various Chinese exchanges (I understand the arguments about fake volume - I just don't think they're relevant for
my purposes.) These days I tend to follow OKCoin for that reason, and Finex and Stamp because any trading I do is likely to be in BTC/USD!
You mention Western traders trading on Chinese exchanges - any recommendations? Even for somewhere online such traders hang out...