As a friend and colleague pointed out (thanks, Jaxon!), “balance” does not always mean “equal”. At certain points in our life it may be necessary to focus on one element more than another. These shifts in focus could be daily, weekly, or span years. The point being, people should have control over where they spend their energy.
This is why flex schedules and the like are not as effective as the idea might seem to imply. Some people are focusing on their careers so the balance scale is tipped towards work. For them, a flex-schedule might actually impede their ability to do and achieve what they are focused on. At the very least, it may not be seen as a benefit at all. For others who may be focusing on other parts of their life (family, religious pursuits, community, etc.) a flex-schedule may still seem too limited and thus is still seen as am impedance to life fulfillment.
Some even argue that work/life balance can lead to mediocrity. (http://activerain.com/blogsview/1133010/is-a-balanced-life-a-mediocre-life-) While I might not go that far as to cast judgment on it, I can understand the point. Great achievements often take a great deal of energy and come at the sacrifice of other parts of our life. This can be said equally of work achievements and personal achievements. I know some people who started a family early in life at the sacrifice of a potentially great career. And I know others who have dedicated a great deal of energy to their career at the sacrifice of having a family. Knowing both these types of individuals, both say they would not change a thing. And they have both achieved something very important to them.
It all comes down to values when determining what constitutes balance in our lives. And while values tend to be pretty resilient, life changing events (marriage, kids, illness, retirement, etc.) and age can all shift them around a bit. Thus, someone very focused on their career early in life may shift to focusing on another part of their lives later giving only a cursory consideration to career. Or the opposite can happen.
We all have different values and even within individuals values shift over time. We all want control over how we find a balance between those values. Assuming there is a two-sided scale to our life between “work” and “life” is just too limiting. We are complex beings and the balance scale we operate on a daily basis looks more like a tilt-a whirl than a scale.
Ultimately, whether someone’s life is in balance is up to them. Recognize that work is a part of life and not something separate. Allow your employees some control over finding their own balance. As long as they are meeting expectations and getting you the result you need, where they are focusing the rest of their energy, should not matter.