Up until that line I agreed with everything you said. But hashrate is no indicator of sentiment. Its a delayed indicator of price. Ignoring transaction fees for now, its simple, if price goes down, hashrate goes down and vice versa. Through difficulty, and assuming stable cost/MH, the relationship is linear; for all the reasons you listed above, in general miners will pull the plug if they cant make a profit, regardless of their sentiment, and if there is money to be made mining, it wont take long for people to figure it out. So what deepbit is showing is simply that bitcoin price tumbled. Nothing else. And unless price goes up sharply, hashrate will continue to decline for a while, and it wont go up because of sentiment or wall street journal front page ads; it will only go up after BTC price has gone up and more miners can run their rigs profitably.