According to ScienceDaily in Is Social Networking Changing The Face Of Friendship? the answer seems to be no.  While Social Networks make the risks of perceived friendship much lower, people still much prefer face to face interactions over those that happen on a online Social Network.

"….Making friends can be costly, according to behavioural ecologists. While it might not be a very romantic view of friendship, making new friends involves an investment by committing time and energy to another person in the hope that they will provide reciprocal benefits in the future.

Dr Reader and his colleagues wondered whether online networks are somehow reducing the investment necessary to make new friends by lowering the perceived risk."

I also heard this before, and it was repeated - the average person has ~ 150 friends and acquaintances:

"…Past research by Professor Robin Dunbar at the Evolutionary Psychology and Behavioural Ecology Research Group at Liverpool University has shown that the average person has a social network of around 150 friends, ranging from very close friends to casual acquaintances.".

I've been feeling that Social Networks have been making the idea of friendship too easy - it comes so easily that it means little.  I think it's more important to earn friendship and suggested "rungs" of friendship in the past - but got feedback those systems are already in place on some networks.