1. There is a middle man. But they are not exactly like real individuals. They are other kind of banks ( like Northern Rock) that heavily depend on credit from other bigger Banks! e.g HSBC may grant a loan to Norther Rock considering its excellent credit record and Northern rock sells mortgages to customers. 2. The figures are not just indicative. These are the real losses known so far. Obviously, this could be only a tip of the iceburg. For example, as per todays news UBS has written off more losses and it is now down to $18.4bn!
You can find clearer picture on news. bbc. co. uk/ 1/ hi/ business/ 7073131.stm
