Seriously, there is a dynamic which happened in the Great Depression that may come back. It is the question of what happens when under the mattress is a sensible investment policy.
In that case you get into an underinvestment equilibrium. People won't invest money in anything. Which means that there aren't new opportunities forming, jobs opening up, etc. Which means that things continue going to shit, encouraging people to stay away from investing in droves.
In the Great Depression things were great if you had money. About 20% of the population was better off than they were before. Things were dirt cheap, people were grateful for anything you gave them, etc. Life sucked for the other 80%...
Cheers,
Ben