After years of giving investors the cold shoulder, Amazon.com Inc (AMZN.O) is starting to warm up to Wall Street. The No. 1 U.S. online retailer was unusually forthcoming during its fourth-quarter earnings call on Thursday, saying it will break out results this year, for the first time, for its fast-growing cloud computing unit, Amazon Web Services. “The team … is putting even more energy around making sure we get great productivity around our various fixed and variable investments,” Chief Financial Officer Tom Szkutak told reporters on a conference call.