I am perplexed that people would "gamble" like this. If you are right, you can make money. But sell your principal residence as was suggested above. At least your downside risk is limited to that. If you short bank stocks or reits, be prepared to cover them off including the dividend payments. It is hard to go against the hoard mentality and one better have staying power and ability to meet margin calls as if you guess wrong, you may have to cover the bet.
If the banks go in Canada, you will have alot of other problems. Like a significantly devalued Canadian dollar. Are you going to invest in foreign currencies as well or buy gold. One thing is sure in a disaster, you will become very wealthy, or get wiped out. For most of us, we would not be too inclined to play that game. If one does this, I hope they do it with a small amount of money they can afford to lose, and not open ended "short selling". But then, I am too conservative but I find it easier to talk about what I did not make than what I actually lost. Most people's risk tolerance rapidly dissipates in the face of real monetary losses.