I say it helps productivity. The temptation is just too great, and limiting it helps. It's really easy to piss away a few hours on the Internet when you could be doing something productive.
I'm all for checking out CNN at lunch, but why allow Facebook, etc.? It's the company's time. Do that stuff at home.
This is spot on.
While we're at it might as well get rid of all the phones. The temptation is just too great to call a friend or spouse or GF or set up a doctors appointment. Better get rid of posters and paintings. Damn employees might be tempted to look at those and waste time. Better not let people sit too close to each other. Too much temptation to talk about non work related things on company time. Better cover up all the windows. Too much temptation to see whats going on out there.
While the comment that you consider to be "spot on" is technically correct, it's a very lazy form of management that won't work anyway because you are not actually addressing any sort of problem. You are putting a band aid over a bullet hole. Eventually you will have to actually speak to your employees about their specific productivity level if you want actual results. Oh no, the horror. Talking to someone about a problem.
There is nothing that infuriates a work staff more than when a blanket rule gets put into effect because one idiot was doing something they shouldn't have been doing. If Sally Smith spent 9 hours on Facebook and didn't do any work, yet your way of addressing that is to get rid of Facebook, I promise you that is a management style that will NOT get the best possible productivity out of the employees.