Personally, I kind of think that we'd see a drastic bounce-back of the market to compensate for such a drop. I haven't run the numbers recently, but I'd estimate that anywhere above $1.25/btc, I would remain profitable mining. I can't imagine it dropping to $1.25 and not bouncing back. There's too much support here. Too many people who believe in the idea for it to have a complete spiral to the bottom, at least when looking at it from the perspective of a panic-sell situation.
I know I'd probably be lining up to buy bitcoins if they were only $1 each again.