Adaptability, health, renewable energy and good balance
The human being has a great capability of adaptation and I believe that is feasible to work on environment like that, however, not for a day long basys. Perhaps it could be pratical in intervals during the day on working stations that could be shared with co-workers.
Despite the fact that it can be beneficial to health in general and agreeing with other comments, for sure it is not for everyone.
Now, thinking green and renewable energy the treadmills could at least generate energy to power its batteries... well I am not an engineer... this is only a thought.
All in all, a good balance between walking and seating for a day-work routine, could be a good approach to spread out this idea. I would be willing to try it, don't you?