The IRS referenced FINCEN in it's report.
http://www.irs.gov/pub/irs-drop/n-14-21.pdfVirtual currency that has an equivalent value in real currency, or that acts as a
substitute for real currency, is referred to as “convertible” virtual currency. Bitcoin is one
example of a convertible virtual currency. Bitcoin can be digitally traded between users
and can be purchased for, or exchanged into, U.S. dollars, Euros, and other real or
virtual currencies. For a more comprehensive description of convertible virtual
currencies to date, see Financial Crimes Enforcement Network (FinCEN) Guidance on
the Application of FinCEN’s Regulations to Persons Administering, Exchanging, or
Using Virtual Currencies (FIN-2013-G001, March 18, 2013).