The traditional time-based billing model is tough to uphold when developing online campaigns, says rich Silverstein, co-founder of goodby, Silverstein& partners, an agency owned by Omnicom, the global marketing giant. 全球营销巨头goodby,silverstein&partners的联合创办人里奇希尔斯坦(richsilverstein)表示,开展在线宣传活动时,很难坚持按时间收费的传统模式。