That's a lot of money. What is this $1 billion being used for? Is this money just circulating for the sake of making more money, or is it being used to buy goods and services?
But, bitcoins are being used in commerce too. New merchants added every day. I know of at least 6 brick and mortar businesses in Las Vegas alone that have sprung up recently.
Stack-exchange for others who want more info: http://bitcoin.stackexchange.com/questions/845/what-are-bitc...