Isn't that how it starts though? It is no longer possible to disrupt Facebook on its terms. You have to offer something completely different at first then slowly add Facebooks key features to provide a smooth transition.
Is there a precedent you're referring to? Because I believe all of the above social networks started as... social networks.
"Innovator's Dilemma" describes a similar process. An underdog comes along, creates an inferior product or a product addressing slightly different needs, and then slowly but surely builds up its feature set to address the big dog's other customers.
Again, where's the precedent in the world of social networking...
What does it matter?
I thought Facebook stared as as a hot or not clone for Harvard students.