The main problem I have with these kind of 'studies' is the presumption that the time used is actually taking away from something.
If your job involves sitting at a computer (this being the kind of job that would allow for frequent diversions of the likes of facebook), then for the most part, your job is probably task oriented, which means that you should be measured by the tasks you complete, and not so much by how much time it takes you (or how much time you might use browsing, or getting a snack, or getting a smoke, or talking to co-workers).
There is no 'magical' ideal of productivity that will be achieved if we all put our noses down and work unceasingly. If you're working, you almost always have a specific job (or set of jobs) to do, and you either do your job(s), or you don't. That's it.
And especially in some creative jobs, there will be times where it may look like you're doing nothing at all, but you're thinking about your task, or you're taking your mind off of it, so that your mind can get around it while you aren't looking (It's pretty amazing how many problems get solved when you aren't actively *trying* to work on them).
This is just another 'numbers out of the ass' kind of analysis. Even if they removed every avenue of distraction, and stood over these workers with a gun to their heads, they would not reap the value they claim to have 'lost'. As a point of fact, in that case, they will more than likely lose productivity.