The questions typically are (1) Can you find an instrument that lets you bet on the mispricing (2) do you have the wherewithal to stay solvent for the arbitrary period of time it takes for the market to correct.
Individual investors typically cannot access the right instruments (typically weirdly structured long term options). Typical institutional money managers cannot because their measurement typically penalizes continuous money loss. Lots of them however may have spotted the opportunity.
They can - just buy an put on the ETF via your favorite neighborhood broker like schwab, etrade, etc.
Getting authorized for options trading on your account is pretty straight forward and serves as a last fair warning of how much money you're likely going to lose :)
EDIT: to clarify, most of the "exotic" stuff like VIX and XIV (was) are ETFs that are accessible by "regular" investors and hide away the complexities of properly structuring the underlying position to get the exposure to certain aspect of the market. This opaqueness is what makes them so dangerous IMO.
Andrew Gelman once mentioned that Black Swan events are actually routinely _overpriced_ via the Longshot Bias. [1] He had talked about this in the context of the recent Leicester FC win and the odds on that team. [2]
