I agree with this so far, but to be honest is an apples to oranges comparison. I dont think 'micro-blogging' i.e. Twitter is a particularly good example of 'social' computing. Unless you go to a 'Tweet up' and actually meet people, and I doubt very much I will ever meet the majority of the hundreds of people I follow. FB however is social in nature. You normally make connections, at least first, with people you really know. Its also a replacement for email messaging for some of may younger friends. Its also an 'application platform' - my wife uses it as much for playing games with her friends who live on the other side of the world as she does for 'talking' to them. So yes, Twitter 'use' may overtake FB use, but so what ?