I swear I am not trying to be a jerk, but I have heard this way too many times but have never seen this succeed in a way which adds to the service. Most of the times the paid premium feature is "no ads" or less wait times etc. Especially for a social networks, I can't even imagine what feature you can build which will make me pay you to be in touch with my friends.

One point against my argument might be reddit gold kind of stuff. They are more of a status signal. You can monetize status signals.