Mayor Bloomberg can count himself amongst the top echelons of the extremely, extremely rich, as Forbes's list of the 400 Richest Americans places him in the #8 position. The magazine cites his purchase of a 20% stake in his company, Bloomberg LP, as how they value his net worth to be $20 billion. The next richest New Yorker is David Koch, at #9 with $19 billion. Some others: Rupert Murdoch is #47 ($6.8 billion), Ralph......