Judging from the Y axis values, that isn't a log chart. And even if it were, small movements at the bottom of the chart are perfectly visible.
Depends on how exactly the y axis is set up. But the point is moot because you're right, the scale is linear.
The only possible narrative to draw from that chart is that Bitstamp volume is flat while Gox volume is decaying to match it. I interpret the approach to this limit as speaking to the meager arbitrage volume between Gox and Bitstamp. Which, given the depth of Gox's order book does not bode well for Bitstamp. It means that Bitstamp is beholden to this arbitrage volume during both high and low volume periods.
Or is it?Arbitrage volume is low because there's not enough profit/too much risk due to the fiat cashout delay on mtgox, plus the actual risk (real or not) of insolvency. I see (mtgox) order book size as mostly unrelated to that, it's a combination of fiat being stuck on the exchange, mtgox historically being the preferred exchange for large traders, and money sitting on the sidelines by those who are out of the loop/simply not interested in the mtgox metagame. Bitstamp order book on the other hand always had a decent sized ask side, but bid size was and is meager. There will be a tipping point where the advantage of the higher depth on mtgox will no longer outweigh the benefits of higher (and more consistent) volume on bitstamp -- only then will market depth on bitstamp match its volume. If mtgox fixes their shit before that point is reached, bitstamp will probably remain secondary, but I don't see any improvements on mtgox so far. ("10 wires per day." Really?)
