I guess it depends on the company, too, as well as whether you are satisfied with your employees work results. If it is a smaller IT company, you most likely have a family like friendly atmosphere where the employees simply enjoy working and being part of an awesome team. In that case, I don't think it makes any sense. But to me it also raises certain privacy concerns. I mean is it ethical at all to watch someone without their knowledge or consent? Even if a worker seems to waste too much time on social media which begins to be detrimental to his or her job quality, wouldn't you warn them or inform them first?