On the borrowing side, households ended up with some assets – like shares in money market mutual funds – that weren't as liquid as they were thought to be; when money funds began to worry about the liquidity of their assets, like asset-backed commercial paper, and when households and businesses tried to use their perceived liquidity, the resulting fire sales accentuated asset price declines and transmitted problems from one sector to another.
The initial problems from the excessive risk buildup were exacerbated by the deleveraging that followed, including in the financial sector. Although there are many reasons that the deleveraging process has been so painful, one of the defining characteristics has been a sharp increase in uncertainty.