Mayor Bill de Blasio recently discovered, during his short-lived campaign against Uber, that saying no to a popular, convenient new technology doesn’t tend to win many friends—or win much at all. In just a few years, New York City’s regulated yellow-taxi fleet has been outnumbered by a distant company with uncertain intentions. There are benefits to this, as well as mounting costs. But critics like Mr. De Blasio won’t get very far until they have something to say yes to.

Uber’s ascent came in the midst of an idealistic surge of companies that dubbed themselves as being part of the “sharing economy.” Through them, many of us have found new ways to share cars, apartments, toys, and time. For all the things that companies like Airbnb and TaskRabbit allow us to share with each other, however, ownership and governance are not on offer. This is what the democratic promise of the Internet has come to: a democracy of access, of “collaborative consumption,” but not of control, real accountability, or ownership.

Companies like Uber now tend to describe what they do as the “on-demand economy” rather than “sharing.” But there is also a movement underway to create a real sharing economy online, one in which people can truly co-own and cogovern the platforms they rely on. This means bringing together new technology with the long history of democratic, cooperative enterprise. This movement, which we call “platform cooperativism,” is something to which Mr. De Blasio might say yes. And in New York this November, we’re gathering the movement’s leaders for the first time.

Taxi drivers in Denver and the suburbs of D.C., for instance, have set up cooperative companies and control their own hailing apps. In New Zealand, the worker-owners of Loomio produce a decision-making platform now being used by governments, schools, and communities around the world. With the help of Janelle Orsi of the Sustainable Economies Law Center, a company called Loconomics is building a worker-owned alternative to TaskRabbit. Home-care workers throughout the five boroughs, in an industry increasingly reliant on online platforms, are talking about creating fairer apps of their own. In none of these cases is technology the savior; what matters is how people organize around it.

The New York City Council has already made historic investments in developing sustainable, worker-owned businesses over the past few years. Perhaps Silicon Alley can show the world how to practice democracy online in ways Silicon Valley never has, connecting the city’s vibrant startup scene with experience from the worker-owned cooperatives already flourishing in Sunset Park and the Bronx.

The authors are co-organizers of “Platform Cooperativism: The Internet, Ownership, Democracy” at the New School on November 13-14.

This movement comes at a moment when ever more of the economy is moving away from the full-time, lifelong employment relationship, toward freelancing and independent contract work. Eighty percent of large American corporations are planning to substantially increase their use of flexible workers in coming years. A report by the Freelancers Union and Elance-oDesk found that there are currently about 53 million independent contract workers in the United States, and this number has been projected to rise to 60 million by the end of the decade.

Online platforms have shaped this reorganization of work underway, serving as bottlenecks for emerging labor markets. They grant workers new kinds of flexibility, but they also allow employers to act lawlessly and hire and fire much more freely—at great cost to people living paycheck to paycheck. Over the long term, whoever owns and controls these platforms will determine who benefits from the emerging future of work.