How important is it for employees to work together physically in the same space?

For Marissa Mayer, the chief executive officer of Yahoo! Inc., it's a deal breaker, according to an internal memo that is generating a raging debate. Starting in June, Yahoo employees with work-from-home arrangements will be required to start schlepping to the office.

"To become the absolute best place to work, communication and collaboration will be important, so we need to be working side-by-side," writes Jackie Reses, head of HR. "That is why it is critical that we are all present in our offices."

E-mail and Skype may appear to be poor substitutes for face-to-face collaboration in the office. But the Yahoo mandate risks alienating workers who depend on a flexible work schedule and ignores increasing evidence that allowing employees to work remotely can increase productivity.

A Bureau of Labor Statistics study last summer showed that telecommuting "seems to boost productivity, decrease absenteeism, and increase retention." According to a Stanford University study released the same day as the Yahoo memo, giving the 16,000 workers at a Chinese travel agency the option to work from home increased productivity by 22 percent. There's also a potential financial benefit: A 2009 Cisco Systems Inc. study found that telecommuting saved the company $277 million a year.

In some cases, working from home means working more. A University of Texas study released in December suggested that employees who work remotely worked five to seven hours more per week compared with those who work exclusively in the office.

Of course, employees are also tempted to sneak in other activities while working at home. According to a Citrix Systems Inc. survey of 1,013 American office workers, 26 percent say they take naps, 43 percent watch TV or a movie and 24 percent admit to having a drink while working remotely. 

That's the kind of data that can really give a manager pause. Even so, Yahoo's new rule just doesn't seem to fit with the new image Mayer is trying to fashion. Last month, she emphasized that mobile is a big priority for the company. Doesn't that also tell her something about the changing nature of the workplace? And is it wise for a tech company competing for top talent to limit workers' flexibility across the board?

We'll know more when Yahoo employees who work remotely begin returning to the corporate nest -- or choose to fly the coop entirely.  

(Kirsten Salyer is social media editor for Bloomberg View. Follow her on Twitter.)