“, with each passing year, Google Inc. and Facebook Inc. are tightening their grip on the online-ad market.That “duopoly” is expected to command a combined 63% of U.S. digital-ad spending in 2017, according to eMarketer, boosting competition among everyone else for what is left. RELATED Meredith Pursues Takeover of Time Inc. That “duopoly” is expected to command a combined 63% of U.S. digital-ad spending in 2017, according to eMarketer, boosting competition among everyone else for what is left.”