I am curious as to how much more productive people will be (if at all) with all the time spent just making themselves look busy, chit chatting, and in meetings. Get your work done in four days. Less time wasted.
Also, i think it would really benefit people if they spent that 3rd day for rest. i know a lot of people that jam pack so much crap into their weekends that they dont give themselves time to unwind.
All my weekend plans are made on saturday (if i am travelling out of town to see friends/family), and i pretty much spend all day sunday without any obligations. That day of no obligations is pretty non-negotiable to me.