PopSugar sees 60 percent of its traffic from mobile. The challenge now is how to make money off it. With its fashion search engine, Shopstyle, mobile converts at only one-third the rate as desktop. The story’s not as bad but not great with its media business. Part of the reason, CEO Brian Sugar said, is that display advertising doesn’t work in mobile. In fact, PopSugar wants to rid its site of mobile banner ads by the end of next year.