Financials can do it. I still believe they will rather create hyper inflation than tighten the money supply thus keep the market moving higher but central bankers could b=very well do the opposite. Up to this point they have been inflating but as more and more institutions need funds from their own stupidity the central bankers can actually tighten the money supply just as they have done prior to the 1929 crash and thus crash the markets.
There are many baby boomers about to retire and that will cause huge problems for the government. A market crash could eliminate a lot of the middle class, consolidate many financial institutions into few mega banks or corporations, eliminate much of middle class and create a society more dependent on government(s) for their livelihood thus allowing the government to pass any law they want.
Either theory holds water but which way the bankers direct things only time will tell and holding physical and investment in PMs is the safest thing at present as there are no solutions to this mess right now - they might prolong it but can't solve it. Let's remember American debt of 9.4 trillion that's still growing <- hyper inflation would solve that ;)