Everyone changes friends as they get older - it's natural. You move away, change interests, move to a new school or University, get a new job, and meet new people. Your friends list on Facebook expands, and as the years go by, the friends you used to talk to every day in high school are a distant memory.
Or are they?
Every so often we'll see a status update from someone and think "Who on earth is that?" It'll take a few minutes to remember that this person used to be one of your closest friends in your second year of University - then you got involved in different societies, you both graduated, she moved hundreds of miles away, got married...you exchanged Christmas cards for a while, but then the contact slowly melted away.
So why do you need to know about what a great time she had on holiday? You have nothing to do with this person anymore. Why are they even on your news feed?
That is the definition of residual friends. They're people we keep on our social networking sites, either through politeness, or simply because you forget you have them on there. You've drifted apart from these people, yet you still get an insight into personal details of their lives, simply by logging in to a website.
But do we need this? Some people will admit that they enjoy spying on other people's Facebook profiles, just to see what they've been up to since they stopped having as much to do with them. They'll browse through their photos, friends, statuses, profile pictures...can we justify this method of, for want of a kinder word, stalking?
On the one hand, if this person has, albeit passively, chosen to remain online friends with you, they've agreed to continue to share their details with you, and social networking is all about knowing about people, isn't it? However, you know you're not actively involved in this person's life - if you liked this person's update, what would their reaction be when they saw this? Would they shrug it off, or would they have to take a minute to remember who you are, then wonder why you're still sticking around to like their stuff?
Perhaps this is the key question one has to ask oneself - how would they feel if you actively interacted with them on the site, whether it be liking a photo or instigating a chat, and vice versa? We've all experienced the person who suddenly pops up, liking photos of you from years ago, and you feel a little creeped out when you realise you have someone browsing through your stuff who you barely spoke to at your last job and only added out of politeness.
If you can't let go, what's stopping you? People regularly have a Facebook friend "clean-out", where they get rid of the people they don't actually talk to. And this can have the same effect as giving your house a good clean - everything seems clearer, and you've got access to the essentials, not the extra stuff you've become bogged down with. You don't have to know what your old friends from ten years ago are up to, if you have no contact with them anymore, so why clog up your newsfeed with such non-essential information? People move on and create new social networks in their real lives - maybe it's time we did this in our online lives, too.