Do we need social networks? I do not think so. This might sound fairly drastic which I am aware of, but let me explain how I came to this conclusion, network by network:
Obviously the biggest and most used one. Almost everyone in the first world has a Facebook account (if you do not count Russia, here purely to state my point, no other implications). Markus ‘Notch’ Persson (the Minecraft inventor) said Facebook was creepy, which I think we all can agree on.
There is a really nice post by Alex Gaynor here about why Twitter is bad as concept, stating mainly that is does not allow effective community forming and promotes harassment. My personal addition to this would be that it is horrible to use and as a not even subculturally known person like most of us it makes little sense to broadcast our thoughts into the void. It also suffers from tweet-spam.
Well, aside from a very small group of people who are mostly into OSS no one is really using it. Everyone with a Gmail-address and/or and YouTube account is involuntarily part of it. Google already has loads of data about everyone, through Analytics, Adsense/Adwords, YouTube, Street View, Android, Chrome and of course the search, simply called Google. They do not need Google Plus, and we do not either.
Reddit is not really a social network, but more of a collection of forums and link aggregators, grouped by topics. Reddit in my eyes is the perfect example of a community-based website done right. The whole voting system for both posts and comments and the mini-communities allow effective, centralized news sharing and discussion for people with shared interests.
Where am I going with this?
There are some more networks and network-like websites, but I do have a point to make. You do not need a network without a community or content. Have a look at YouTube. There are subcommunities, like the gamers, the beauty-girls, the comedians, and others, and there is content in the form of videos. Hackernews is a link aggregator which focusses on computer geeks, an existing community, and content in the form of links (most of the time).
The first three networks on our list are networks just to be networks. Facebook aims to be omnipresent and allow you to contact your real-life friends while also incorporating sites to follow celebrities or companies. This actually makes sense, and it obviously works. Twitter and G+ are just empty networks that allow people to interact, but no one told them why they should. Facebook works, because everyone uses it. But ultimately, you do not need Facebook to contact who you know anyway. When the time comes and people are less obsessive about sharing how cool their life is, Facebook will go down.
People live without Facebook, and they continue to do so. People you are interested in have your number. Anyone on the internet you might want to interact with is probably a member of a community you are a member of as well. Reddit does this, 4chan, Hackernews, IRC and even mailinglists do this. Facebook, Twitter and G+ do not.