[deepak56]

"By that standard, practically any online service or platform these days is a social network!" Yes, but to me, this is the correct standard anyway. Two reasons: a) My time is limited: Anytime I spend on something like Medium is time away from Facebook. They are all competing for that limited time I have for being involved in a social network. and b) All these services generally also mean a different set of friends for the me. There is some overlap but almost all my social networks have a different group of followers/recommenders etc. The more time I invest in building one set of friends, the less I do in another - and this is a sticky investment, one that can easily prove make or break for any social network.