Critics have derided WeWork as overvalued and vulnerable to the next downturn. But the company holds so many leases in so many cities, it might hold more power than its landlords.

Real estate titans have long scoffed at WeWork, which in eight short years has managed to attain a $20 billion valuation by selling short-term leases for shared office space with a mixture of stylish design and free-flowing alcohol.

Derided by some as a real estate company masquerading as a technology company, it has been called everything from a “$20 billion house of cards” to a “Ponzi scheme.”

The naysayers argue that WeWork’s business model looks brilliant only in a rising economy that has allowed it to lock in long-term leases and then re-rent that space to other businesses at a premium. The enormous valuation it has obtained is higher than that of Boston Properties and Vornado, two of the country’s biggest office-space landlords — companies that actually own the kind of space that WeWork usually rents.

Now, with interest rates creeping higher, residential real estate prices flattening and fears of an economic slowdown coming, real estate insiders are gleeful at the notion that a downturn could be an existential threat for the company.