Governments may not allow banks to deal with bitcoin as with fiat it is necessary to show source of funds if above a certain amount. Bitcoin is anonymous transaction so deals cannot be traced.
If I think the future predictions of bitcoin and a number of other digital currencies will one time replace the position of paper money as a medium of exchange. The reason, this currency can fix problems that exist in paper currency, and indeed in history, the same thing always happens in the new currency that replaces the old currency. For example, gold replaces barter systems as a means of transactions, and paper money replaces gold. Now, bitcoins and some other digital currencies will replace paper money as a means of transaction.