Quoting a recent email of mine...
With bitcoin, every transaction is written to a globally public log,
and the lineage of each coin is fully traceable from transaction to
transaction. Thus, transaction flow
is easily visible to well-known
network analysis techniques, already employed in the field by
FBI/NSA/CIA/etc. to detect suspicious money flows and "chatter." With
Gavin, bitcoin lead developer, speaking at a CIA conference this
month, it is not a stretch to surmise that the CIA likely already
classifies bitcoin as open source intelligence (no pun intended).
Attempting major illicit transactions with bitcoin, given existing
statistical analysis techniques deployed in the field by law
enforcement, is pretty damned dumb.
It is well documented in the press that intelligence agencies observe "flows" of money and intelligence. Bitcoin, with its open and visible transaction history, is definitely open to that same sort of analysis and observation. So, I would presume that there is plenty of existing software out there to handle this sort of thing.