The document discusses the evolution of real-time bidding (RTB) for online advertising. It describes how RTB has provided higher revenues for publishers compared to traditional ad networks and increased control and transparency. It also outlines how programmatic buying and selling of digital ads continues to grow and will make up the majority of online display advertising spending. The use of RTB has increased dramatically from 0% to over 50% of ad spending on some platforms between 2010 and 2011.