Re: Wasting twice the time
I agree that the likelihood is that much of time spent on facebook has been appropriated from other leisure or low productivity time but there is also an argument that it has impacted on other areas of the economy by allowing free broadcast and communication technologies to the masses, thus eliminating the need for those service sectors.
One example is all those birthday wishes which many moons ago would have come in the form of a card, made by a stationary company, sold in a shop and delivered via a postal service now comes in the form of a wall post.