I'm a strong proponent of allowing people to work from home, but I have also had conversations with people in the past about whether its appropriate for them. Ultimately it needs to come down to the question of whether people are getting the work they need to be doing done, and if not whether that's for reasons outside of their control. If people are delivering what they need to be delivering (whether that's in the way you'd typically expect or not), there isn't a problem. If they aren't delivering, that's the problem to solve, not the nuances of a work from home policy.