Why is an upward shift in mining power a signal of Bullishness? Someone? Anyone?
Presumably, each person mining seriously on GPUs (where power costs are a factor) is looking for some minimum "real dollar" value per hash to make running their rig (and paying those bills) worthwhile. So, presumably, miner beliefs that the price is going up = more miners firing up their rigs = upswing in total network hashpower, and miner beliefs that the price is going down = more miners mothballing their rigs = downswing in total network hashpower.
Of course there are other factors that go into this kind of math (for instance, the current difficulty, which just got reduced a couple days ago). But expected electricity return on BTC (i.e. expected exchange rate) is definitely one of them.