Bitcoin payments processor Coinbase on Monday opened a regulated exchange in the United States for trading the virtual currency, the company said. Coinbase users in 24 states and U.S. territories can immediately trade on the exchange, which will charge no fees through March 30, according to a blog post by the San Francisco-based company. http://www.reuters.com/article/2015/01/26/us-usa-bitcoin-coinbase-idUSKBN0KZ2CH20150126 marc