It's not just that. Low volume is an indication that the actual Bitcoin economy isn't running. The only activity I see on the depth window are the last remaining trading bots. I mean, how is someone supposed to get a few bucks into MtGox to buy something on SilkRoad or wherever? The Bitcoin price went from being 99% speculation, to being 99.999% speculation. I'd love to know how SilkRoad sales have been impacted with the closure of LR, MtGox-Dwolla, etc... At this rate, it's a long long way down...
I follow
r/SilkRoad for a bit of insight into that economy, and outside of vendor reviews, the most frequent problems posted relate to getting money into coins. Many are using BitInstant and Coinbase now, but there are other more underground services, such as Blue Sky Traders, that are also popular.
I'm not aware of an accurate way to gauge the volume on SR or BMR, but I don't detect a falloff in the anecdotal stats I check. SR had significant downtime about a month or so ago though.