Some people buy bitcoins as an investment, hoping theyll increase in value. There are many online marketplaces that allow people to buy and sell bitcoins using different currencies. Coinbase, in San Francisco, runs the worlds largest bitcoin exchange, and operates 2.8 million bitcoin wallets globally, according to Wired. You can also buy and sell bitcoins on Bitquick, Xapo, and CoinCorner, among other exchanges.