Without your knowledge, somebody, somewhere may have just "unfriended" you.
Unfriending is not uncommon, but why are people so quick to cull?
Pew Internet research found that six in 10 people have unfriended someone on Facebook.
A study by Christopher Sibona of the University of Colorado Denver investigated the psychology of this unfriending.
The study looked at why people unfriend and how the unfriended feel about it.
Researchers recruited participants using Twitter. The respondents had to identify the last individual they unfriended and give the reason why.
A total of 2865 people began the survey, with 1552 completing it, wrote Sibona, a doctoral student in computer science and information systems.
It turns out that we are most likely to unfriend high school friends, followed by an undefined category, friends of friends and lastly work colleagues.
"These four friend types account for the majority [53.7 per cent] of unfriending decisions," Sibona wrote.
The main reason school friends are unfriended is because "the person posted polarising comments often about religion or politics", Sibona says.
Posting frequently about unimportant topics was another factor.
While old school friends are unfriended because of their online activity, the study found that work friends "were more commonly unfriended for disliked ofﬂine behaviour".
However you know your contacts, Sibona says there are four main types of posts that are likely to lose friends.
"The four online reasons were frequent/unimportant posts, polarising posts [politics and religion], inappropriate posts [sexist, racist remarks, etc] and everyday life posts [child, spouse, eating habits, etc]."
Rachel Way, a small business owner, said the last person she unfriended was a friend of a friend.
"I unfriended him because he was constantly boasting about an unfair dismissal case and it was doing my head in."
Joel Attenborough, a hot sauce importer, says he has unfriended people "who post ignorant, racist, sexist, homophobic comments".
Turning the tables, researchers found those who have been unfriended experience a range of emotions.
The most common response is "surprise", followed by feeling "bothered", "amused" and "sad".
Attenborough says he has probably been unfriended but he doesn't know when or why.
"I haven't noticed, so the relationship couldn't have been that good to begin with," he says.
Another study, from Birmingham Business School, found that the way we conduct ourselves online affects our relationships in real life.
On Facebook, friendships merge into one large group, with communication between friends visible to other network connections.
"It is the blurring of these otherwise distinct relationship boundaries that causes social tension," the study found.
Results from a sample of 508 Facebook users found that frequent photos shared by a partner could "violate what is expected to be shared between partners and so is related to a decrease in scores of intimacy".
Similarly, sharing photos of close friends also has a negative impact on the quality of the relationship.
Researchers recommend "individuals should adjust their privacy settings" to ensure disclosure of content doesn't harm potential and current relationships.
It seems that focusing on our friends and relationships in real life is the way forward.
In 2010, American comedian Jimmy Kimmel declared November 17 National Unfriend Day. He encouraged people to delete those contacts they hardly knew.
"Half of the people in this country are on Facebook and many of those people have hundreds, if not thousands of friends," he said.
"I find this unacceptable; that no one has thousands of friends . . . If you have 10 friends in your life then you're doing very well."
- Sydney Morning Herald
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