Twitter (thanks @kevinmeyers) alerted me to this chart, from the IMF April 2009 Global Financial Stability Report. Kevin's original source for the chart, NPR, reports the numbers represent how all these institutions were linked by credit default swaps. This seems to explain, because of the number of links, and values associated with them, why AIG and Bear Stearns were "too big to fail".
It's Earth Day ... here's something else too big to fail. Let's do something about that.