Thanks for your input Vitalik. Speaking from the Wall Street perspective, not all exchanges out there are even suitable for high frequency trading (witness the recent rise of electronic exchanges - ARCA, BATS, etc). Not all participants are interested in "low-quality" liquidity so to speak, as provided by most high-frequency exchanges (which was one of the indirect causes of the infamous 2010 Flash Crash). Not all assets need to be traded on a real-time basis (real estate [which has many analogies with BTC], bonds, and mutual funds for instance). It's not also widely appreciated that official settlement for stock trades occurs not instantaneously, but 3 days (the T+3 rule). In contrast, 1 hour (6 confirmations) is widely acknowledged to be a reasonable settlement time for even the largest BTC trades.

The blockchain more closely resembles, say, the housing market or the contracts/swaps derivatives markets, which don't operate in any way similar to HFT even though they handle trillions of dollars in notional value. So the notion that non-highly liquid markets can't be valuable is absurd.