“Half the money I spend on advertising is wasted; the trouble is I don't know which half.” Many of us can identify with this well-known lament from John Wanamaker, a pioneer of marketing. He said it almost 100 years ago, but it’s still painfully applicable today. Advertising has become unimaginably complex over the years. There are now so many intermediaries in the supply chain – including programmatic advertisers and ad tech companies – that fraud is increasingly difficult to keep at bay. Read how Blockchain might be able to save the day.