Mark Zuckerberg is set to testify in a landmark social media addiction trial

A business model that has turned likes and notifications into shareholder returns is about to be dissected by 12 jurors.

Meta $META CEO Mark Zuckerberg will take the stand Wednesday in a landmark social media trial, and his testimony will anchor a larger experiment: Can “engagement” be reframed as liability? It's a question that could shadow Silicon Valley for the next decade.

The case in Los Angeles centers on a 20-year-old plaintiff identified as KGM, who says that she began using YouTube and Instagram as a child and that her compulsive use worsened her depression and suicidal thoughts. Plaintiffs argue that the platform's choices were designed to maximize time spent and emotional intensity and that the foreseeable byproduct was damage. And the plaintiffs’ lawyers will point at the product itself — the infinite feed, the recommendation engine, the notifications that arrive like tiny taps on the shoulder — and argue that the point was never connection. The point was compulsion.

TikTok and Snap $SNAP have already settled out of this lawsuit, leaving Meta and YouTube as the remaining defendants and turning this courtroom into a bellwether for thousands of similar claims waiting in the wings.

Meta and Google $GOOGL deny the allegations, leaning hard on a familiar defense: the science is messy, mental health is complicated, and a bad outcome after heavy use isn’t proof of a defective product. Meta has also highlighted safety tools and parental controls, while its lawyers argue the plaintiff’s struggles have roots in personal trauma rather than social media.

But the legal maneuver that has Silicon Valley watching is the attempt to treat social platforms like consumer products with defective design, rather than speech platforms shielded from liability for what users post. Plaintiffs are trying to win on architecture, not content — an argument built to pry open the industry’s most reliable moat. If a jury buys that framing, it moves money beyond one case. It changes discovery, it changes settlement math, and it changes how executives talk about “engagement” in rooms where user metrics can end conversations.

Zuckerberg’s testimony is expected to pull the debate out of abstraction and into the executive suite. Plaintiffs want him on record about what Meta knew from internal research on youth well-being and how it weighed those findings against the business incentives baked into engagement. The defense will want him to look like a CEO overseeing an evolving product, not an architect of addiction.

Whatever the case, this trial feels like a rehearsal for the next decade of tech liability. “Engagement” has always been sold as a metric — neutral, managerial. Now, 12 jurors are being asked to see it as something else: a design choice with foreseeable harm, measured in minutes, optimized in experiments, and monetized at scale.

Silicon Valley spent a decade worshipping engagement. This week, a Los Angeles jury gets to decide whether that metric is a growth strategy — or a design choice with foreseeable harm.