one of the reasons saddam was attacked was because he threatened to change the currency (link 1, link 2, link 3) he was selling his oil in. same with ghaddafi (link).
overstock.com's addition of bitcoin as a method of payment was a great success. in the first day that they introduced bitcoin, they had 840 orders that totaled over $130,000 if converted to the dollar.
overall, bitcoin usage has increased by over 75% in the second half of 2013. when someone uses bitcoin, they don't use other currency. this is a concern for many banks, since they're losing a piece of the pie with the increasing popularity and usage of bitcoin. to say banks have no reason to worry does not make sense when you look at the numbers.