Mark Bergen and Jennifer Surane report:
For the past year, select Google advertisers have had access to a potent new tool to track whether the ads they ran online led to a sale at a physical store in the U.S. That insight came thanks in part to a stockpile of Mastercard transactions that Google paid for.
But most of the two billion Mastercard holders aren’t aware of this behind-the-scenes tracking. That’s because the companies never told the public about the arrangement.
Read more on Bloomberg.