My guest today is Mark Grether, SVP and General Manager of PayPal Ads. Mark has helped shape some of the biggest shifts in modern advertising, from co-founding Xaxis at WPP to leading Sizmek, through its acquisition by Amazon, to helping grow Uber advertising into a billion-dollar global business with more than half a million advertisers. Today at PayPal, he's focused on building an advertising business designed to help merchants sell smarter and consumers discover more of what they actually care about.