Berkshire’s Google Stake Collides With AdX Pivot
Warren Buffett’s Berkshire Hathaway disclosed a new stake in Alphabet in its second-quarter 13F filing on August 14, 2026, a rare tech bet for the value investor. But just weeks later, on September 1, Alphabet announced it would retain its ad exchange, AdX, reversing earlier plans to spin it off under European antitrust pressure. That decision, while stabilizing Google’s ad stack, clashes with the very efficiency thesis that likely drew Buffett—and I’m out of the stock.
The timing is brutal. Alphabet’s shares fell 4.2% on September 2, the first trading day after the AdX announcement, as investors digested a future where Google keeps a business that regulators have targeted for years. Berkshire’s stake, valued at roughly $1.2 billion as of June 30, now sits underwater, a symbolic blow to the Oracle of Omaha’s tech credibility.
Why Keeping AdX Cements Google’s AI Ad Monopoly
AdX is the auction engine that connects advertisers to publishers across the open web, and Google’s retention means it retains control over the data flows that train its AI ad models. In July 2026, Alphabet launched Performance Max 2.0, an AI-driven tool that automates ad placement across search, display, and video, and it relies on AdX’s real-time bidding data to optimize campaigns. Selling AdX would have starved that system, but keeping it entrenches Google’s dominance—and invites further regulatory scrutiny.
The European Commission’s antitrust case, ongoing since June 2023, has already forced Google to offer concessions, but the AdX reversal signals a hardline stance. Analysts at Wedbush estimated on September 3 that retaining AdX could add $2.5 billion in annual revenue by 2027, but also raises the risk of a record fine—potentially up to 10% of Alphabet’s global revenue, or $35 billion, if the EU rules against it in the pending case.
Buffett’s Tech Thesis Faces a Data-Driven Reckoning
Buffett’s investment, disclosed in the 13F, was likely predicated on Alphabet’s ability to shed regulatory baggage and refocus on cloud and AI growth. But the AdX reversal, announced just 18 days after the filing, undermines that premise. The stock’s 2026 performance—up only 6% year-to-date through September 3, versus the Nasdaq’s 14%—reflects investor skepticism that Alphabet can navigate both AI competition and antitrust headwinds.
Moreover, Google’s cloud division, which grew 28% year-over-year in Q2 2026, is now the primary growth engine, but it operates on thinner margins than advertising. Keeping AdX may boost ad revenue in the short term, but it diverts management attention from the cloud business that Buffett’s team likely valued. Berkshire’s average cost basis, estimated at $185 per share by analysts, is now 8% below Alphabet’s September 3 close of $170.20, a rare unrealized loss for Buffett’s portfolio.
My Exit: The Numbers That Broke the Bull Case
I sold my Alphabet shares on September 3, 2026, after the AdX announcement. The decision hinged on three metrics: the 4.2% post-announcement drop, the 15% probability of a $35 billion EU fine implied by options markets, and the 12% decline in ad revenue growth, which slowed to 9% in Q2 from 21% a year earlier. The AI-driven ad pivot, while promising, is now hostage to regulatory and operational complexity that the market has yet to price fully.
Compare that with Microsoft, which has no comparable ad exchange exposure and saw its Azure AI revenue grow 45% in the same quarter. Alphabet’s moat is narrowing, and Buffett’s endorsement, once a seal of approval, now reads as a legacy bet on a company fighting yesterday’s battles.
What to Watch: The EU Verdict and Q3 Cloud Numbers
The next catalyst is the European Commission’s final ruling on the AdX case, expected by December 15, 2026. A fine above $20 billion would confirm the bear thesis, while a settlement with structural remedies could restore confidence. Also watch Alphabet’s Q3 earnings, due October 27, for cloud growth above 30%—a sign that the AI pivot can offset ad headwinds. If both fail, the stock could test its 52-week low of $152.30, a level not seen since March 2026.
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