The way I put it is that lessons learned at th cost of hundreds of billions of dollars tend to stay learned. But Jamie Whyte, as usual, says it better:
And now that everybody knows about the risk, regulation is redundant. The same goes for liquidity risk in mortgage- backed bonds. When no one knew about it, regulating it was impossible. Now that everyone knows about it, regulating it is pointless; the market will now price it in.
In fact, once risks are known, regulating them is worse than useless. It can only move the price of risk away from, and usually above, the market price. That is a recipe not only for inefficiency but for future calamities. It encourages financiers and investors to seek profit in areas where the regulators are not imposing their burdens – namely, those where the risks are poorly understood.