Combined with other recent acquisitions, the Yahoo deal will allow Verizon to track consumers not only on the web, but also at their physical locations, said Jeffrey Chester, executive director of the Center for Digital Democracy, a privacy advocacy group.
Verizon's acquisition of Yahoo's core digital advertising business, "when combined with the capability to gather information from its wireless devices, broadband networks, and set-top boxes, gives it control over the key screens that Americans use today," Chester said by email.
"Verizon’s ability to track a single person across their devices, when they are in a store, at home, work or school, and connect the digital dots to know whether they are now on their mobile phone or home watching TV, is a threat to the privacy of Americans," he added.
Verizon said it takes customer privacy seriously. The company will "continue to comply with existing laws and to honor the commitments we have made to our customers," spokesman Richard Young said by email.
In 2015, Verizon purchased AOL, publisher of popular websites The Huffington Post, Engadget, and TechCrunch, and then AOL purchased mobile advertising firm Millennial Media.
Millennial Media, in 2015 regulatory filings, boasted that it had compiled more than 700 million user profiles, with more than 60 million of them linking mobile devices and PCs to "a single specific user on an anonymous basis."
Verizon's recent buying spree shows that broadband providers are "rushing to supplement their already robust data collection capabilities to better target marketing to their customers with highly personal and comprehensive data," Eric Null, policy counsel for the New America Foundation's Open Technology Institute, added by email.
Null called on the U.S. Federal Communications Commission to finalize its controversial privacy rules that would require broadband providers to get opt-in permission from customers if they want to use their personal information for most reasons beyond marketing their own products. Many ISPs have opposed the proposal.
Chester called on the FCC and the U.S. Department of Justice to "prevent Verizon from taking anticompetitive and unfair advantage of its broadband ISP bird’s nest view of what their subscribers and consumers do -- online and off."
The FCC and President Barack Obama's administration "must ensure that deals like Verizon/Yahoo don’t further erode the little privacy Americans enjoy today when they use digital media," he added.
Verizon has championed the deal as a way to grow its mobile marketing business, and its recent deals give the company more than 1 billion monthly page views, the company said. Verizon is "scaling up to be a major competitor in mobile media," Lowell McAdam, the company's chairman and CEO, said in a press release.