In the comments some are pointing to the reserve requirement of 10% to indicate that the multiplier can not be 100, that it is more in the range of 10. But this fails to recognize that the 10% reserve requirement is only applicable to certain types of accounts such as demand deposits, that other types of accounts have lower requirements and some require zero in terms of reserves, such as nonpersonal time deposits. Here's the Fed chart on it:
|% of liabilities||Effective date|
|Net transaction accounts 1|
|$0 to $11.5 million2||0||12-29-11|
|More than $11.5 million to $71.0 million3||3||12-29-11|
|More than $71.0 million||10||12-29-11|
|Nonpersonal time deposits||0||12-27-90|
Thus, the only way to determine the real multiplier is to forget about looking at the reserve requirement for demand deposits and simply look at required reserves and see what multiple of that results in M2 money supply.
The current required reserves are $103 billion. M2 currently stands at $10.39 trillion. This gives you approximately a multiple of 100 times required reserves to reach current M2.
There are also regulatory capital restraints on banks as to how much money they can loan out, but bottom line with $1.5 trillion sitting in excess reserves, there is a lot of firepower that can be moved from excess reserves to required reserves to could explode the money supply.