In a memo to employees after announcing that Verizon Communications would buy his company for $4.4 billion, Tim Armstrong, AOL’s chief executive, offered a rhapsodic hymn on a single subject: mobile.

The future of nearly all media, and consequently the future of nearly all advertising, he said, is about our phones. “If there is one key to our journey to building the largest digital media platform in the world, it is mobile,” he wrote, by way of explaining why AOL, a company known for its news and entertainment sites and its dial-up subscribers, was merging with a cellphone carrier.

Mr. Armstrong ended his memo, which was otherwise puffed with jargon indecipherable to many outside the world of advertising and media, with a clear message that could double as the catchphrase of his entire industry: “Let’s mobilize.”

His words — and the deal with Verizon he just helped engineer — are just the latest corporate reaction to a staggering shift in the way people across the globe get their news and entertainment. Over the last couple of years, we have collectively decided to use our phones to reach the Internet more than we ever used our computers to do the same thing. And like a horde of aggrieved vultures that has just seen its carrion spirited away to some other part of the savanna, the tech and media business is equally panicked and excited about the vast possibilities for making money from the shift.