I can't say that I am sure yet, but it is very significant that this came from London. London has lax rehypothecation laws, which allows companies to use client funds as their own without their customer's knowledge. In short, JPM was doing the same thing as MF Global, and has likely lost a lot of their customer's money, who didn't know they were taking these risks. Except this is bigger than MF Global.
This is something that can cause a loss of confidence in the system if any more people lose their funds, and cause a market crash.
Well said. If clients start getting antsy and yanking funds (from JPM or others) we could see a repeat of the 2008 liquidity crises that hit the financials.