Then, in March of this year, came a startling announcement: IBM wanted thousands of its workers back in actual, physical offices again.

The reaction was generally unsparing. The announcement was depicted, variously, as the desperate move of a company whose revenues had fallen 20 quarters in a row; a veiled method of shedding workers; or an attempt to imitate companies, like Apple and Google, that never embraced remote work in the first place. “If what they’re looking to do is reduce productivity, lose talent, and increase cost, maybe they’re on to something,” says Kate Lister, the president of Global Workplace Analytics, which measures (and champions) working from home.

IBM might have seen this coming. A similarly censorious reaction greeted Yahoo when it reversed its work-from-home policy in 2013. Aetna and Best Buy have taken heat for like-minded moves since. That IBM called back its employees anyway is telling, especially given its history as “a business whose business was how other businesses do business.” Perhaps Big Blue’s decision will prove to be a mere stumble in the long, inevitable march toward remote work for all. But there’s reason to regard the move as a signal, however faint, that telecommuting has reached its high-water mark—and that more is lost in working apart than was first apparent.

How could this be? According to Gallup, 43 percent of U.S. employees work remotely all or some of the time. As I look to my left, and then to my right, I see two other business-casual-clad men hammering away on their laptops beside me at a Starbucks just outside Chicago. They look productive. Studies back this impression up. Letting Chinese call-center employees work from home boosted their productivity by 13 percent, a Stanford study reported. And, again according to Gallup, remote workers log significantly longer hours than their office-bound counterparts.

Another batch of studies, however, shows the exact opposite: that proximity boosts productivity. (Don’t send call-center workers home, one such study argues—encourage them to spend more time together in the break room, where they can swap tricks of the trade.) Trying to determine which set of studies to trust is—trust me—a futile exercise. The data tend to talk past each other. But the research starts to make a little more sense if you ask what type of productivity we are talking about.

If it’s personal productivity—how many sales you close or customer complaints you handle—then the research, on balance, suggests that it’s probably better to let people work where and when they want. For jobs that mainly require interactions with clients (consultant, insurance salesman) or don’t require much interaction at all (columnist), the office has little to offer besides interruption.

But other types of work hinge on what might be called “collaborative efficiency”—the speed at which a group successfully solves a problem. And distance seems to drag collaborative efficiency down. Why? The short answer is that collaboration requires communication. And the communications technology offering the fastest, cheapest, and highest-bandwidth connection is—for the moment, anyway—still the office.