Amazon Easing Into $1B Sideline Business: Ad Sales

Amazon.com is cautiously dipping into its trove of customer data, trying not to betray consumer trust as it develops a digital advertising business that's on track to sell nearly $1 billion worth of ads this year. The data the retail giant collects on its 237 million active customer accounts puts Google to shame. Amazon doesn't just know what folks have searched for, it knows what they bought. Using that data has turned Amazon into one of the web's ad juggernauts, the seventh-largest seller of digital ads worldwide, according to eMarketer.