There is term that global banking regulators have been talking about, since the Federal Reserve Bank of New York in 2008 “generously lent” AIG $182 Billion, the term is known as The Shadow Banking System.
[It was Tim Geithner the former US Treasury Secretary who was the head of the New York FED in 2008 that approved the AIG rescue].
Princeton academic Paul Krugman is the economist who coined the term, The Shadow Banks.
[http://www.amazon.com/Return-Depression-Economics-Crisis-2008/dp/B0051BNVIG/ref=sr_1_1?ie=UTF8&qid=1318576098&sr=8-1]
Within the market-based financial system, “shadow banks” are particularly important institutions. Shadow banks are financial intermediaries that conduct maturity, credit, and liquidity transformation without access to central bank liquidity or public sector credit guarantees. Examples of shadow banks include finance companies, asset-backed commercial paper (ABCP) vehicles, limited-purpose finance companies, structured investment vehicles, money market unit trusts, securities lenders, and even supermarkets, UK has Tesco Bank and Sainsbury’s Bank for example. All are able to take deposits and enter the financial market and trade.
Shadow banks are interconnected along a vertically integrated, long intermediation chain, which intermediates credit through a wide range of securitisation and secured funding techniques such as ABCP, asset-backed securities, collateralised debt obligations, and repo.

This intermediation chain binds shadow banks into a network, which is the shadow banking system. The shadow banking system rivals the traditional banking system in the intermediation of credit to households and businesses. Over the past decade, the shadow banking system provided sources of inexpensive funding for credit by converting opaque, risky, long-term assets into money-like and seemingly riskless short-term liabilities. Maturity and credit transformation in the shadow banking system thus contributed significantly to asset bubbles in residential and commercial real estate markets prior to the financial crisis of 2008.
In essence, a failure in a Shadow Bank like AIG would have hadmassive effects, such as contagian, or US savers with 401k plans loosing life savings, so regulating these institutions is a key issue that governments and regulators are trying to address.