Employees who avail themselves of workplace flexibility options often suffer setbacks to their careers, in the form of wage penalties, lower performance evaluations, and fewer promotions, according to the Center for WorkLife Law. That may explain employees' reluctance to take advantage of flexibility programs, despite the fact that they have become more widespread: Only 11 percent of full-time employees have formal flexible-hours arrangements, and only 18 percent have informal arrangements.

"Many times these policies are on the books, but informally everyone knows you are penalized for using them," said Joan C. Williams, founding director of the Center for WorkLife Law. Williams coined the term "flexibility stigma" to describe this phenomenon.

Mothers, she says, are hit particularly hard with this stigma, but men can't avoid it either. A study recently found that men who took leave after the birth of a child were more likely to be penalized and less likely to get promotions or raises. Another study found that when highly qualified women requested leave or a part-time schedule, their status fell sharply, as did the quality of their work assignments.

The dilemma is that work flexibility options, such as telecommuting and compressed work weeks, are becoming more common as organizations grow more demanding and complex. So even as employers extend such offers, they expect employees to be assuming ever more responsibilities—especially at the highest levels of organizations.

If employees have to worry about work-life balance, they won't be considered for top jobs, says Randy White, co-author of Breaking the Glass Ceiling: Can Women Reach the Top of America's Largest Corporations? Securing senior positions requires high levels of visibility—which simply can't be achieved if employees are simultaneously negotiating their work-life boundaries.