Is there any measure of how much was exchanged out of ETH? If you wanted to pump that number up all you need to do is create lots of wallets and transfer ETH amongst them.
Look @ http://coinmarketcap.com/
Are you referring to the strategy of placing and canceling limit orders that were never intended to clear?
I think it's just a matter of your definition of liquidity. If you use a trading strategy that assumes that all limit orders will remain there for 10 full minutes, you might turn out to be wrong, and if so your notion of the liquidity of the market will be wrong.
Liquidity is misleading in the same way that price is misleading. The price is the last price that a single unit was traded. Liquidity is the typically thought of as the supply or demand for additional transactions at or near the last market price, or a notion of how stable the price is to fluctuations in supply and demand.
The more volume that trades at a price, the more real that price is. An unfilled limit order contains zero price information, so anyone using it as information should be wary. It may be wishful thinking (typical) or a feint (in the case of some HFT strategies) but it is not evidence of a clearing price unless it clears.
Of course, the same applies to cryptocurrency prices. I spoke with someone who runs a big desk recently and was pretty surprised at how close he was able to come to "market price" for very large transactions.