Whatever implications social networks have on society, it's clear that they are here to stay.
Facebook has become HUGE. Many of us avoid it for various reasons. Others spend way too much time on it. Still others see it as a useful tool.
Lately I've gotten the idea that while Facebook has successfully captured the attention of an absolutely huge worldwide demographic, it's pretty limited in terms of functionality and professionalism. All of your friends are just that - 'friends'. It's impossible to sort people by category, which (I would think, anyway) would be more or less essential for any sort of professional-level social network that wants people to take it seriously.
Facebook allows the quick dissemination of personal information, but it does not allow the user to control the manner in which it is disseminated very well. If you want to share something on Facebook, you (basically) have two options: make it public, or make it friends-only. Unless, that is, you want to painstakingly select which people can see it by designating them one by one.
This could all be cleared up by categorical social networking.
Sort your contacts into 'Casual Acquaintances', 'Business Contacts', 'Family', 'Close Friends', 'Fellow Students', 'Coworkers', 'Customers', 'Online Friends', ... et cetera. It seems almost unbelievable that Facebook doesn't already allow people to do this so that users can easily decide just who gets the messages they're sharing. More importantly, this sort of 'aimed sharing' would let the social network truly expand into the commercial world.
(Removing language like 'poke' wouldn't hurt, either.)
Additional levels of privacy amongst various categories should also be a priority for a next-gen social network. All of the people in my 'Casual Acquaintances' should not be able to know that I am best friends with User X, or that I am a business contact of User Y (if I don't want them to, that is). Facebook's open-book tendencies are a huge stumbling block to professional use of the network.