The global black market capital flow has been estimated around $20 trillion and growing at faster rate with the widespread trend towards financial facism (cash limits, bank account monitoring, capital controls, financial data mining, etc).
In my research I discovered, and this is not a secret, that bitcoin already has a big demand, and spending, its just that not that maninstream yet.
◘The biggest economic industry in bitcoin is the gambling one no doubt, all these casinos popping up and dice sites, they probably hold most of the bitcoin cashflow.
(Seeing satoshidice or primedice transactions of 500 BTC moving around all day)
I guess the top Bitcoin exchange (by daily volume traded) has Bitcoin cash-flow times greater than all Bitcoin gambling sites taken together. You just won't be able to see the bitcoins at these exchanges moving (changing hands) 99% of time...