One thing worth noting is that, unlike in GPU times, power costs are comparably much smaller with ASICs and in most cases people will keep their miners online even if their profit is rather negligible.
Maybe for the usb models but most of the ASIC machines use standard pc power supplies using anywhere between 600w to 1200w, before I moved my farm into a datacenter I was spending over $300 a month on power running my ASIC machines.
One interesting factor that I've started to notice is when the price of BTC falls more than 10%, some of the pools show a major reduction in hashing speed then go back up when BTC rises again. As an example, the pool speed at BTC Guild dropped more than 500Th/s within a couple of hours of the BTC price dropping Friday. While I'm just speculating, I'm guessing the large mining farms shut down production when BTC drops to cut power costs.