That guy you met on that work experience week back in 2004? Notable overbite, always wore green jumpers? You added him on Facebook out of sympathy and have ignored him ever since?
It turns out that should Kevin (or any Facebook contact you barely recall) post about his political leanings, there's an exceedingly high chance you'll unfriend him.
I Don't Like You Anymore, a superbly-titled research paper by the Hebrew University of Jerusalem, found that weak Facebook ties were more likely to be broken in response to politically-themed posts that didn't line up with personal leanings.
Published in this month's Journal of Communication, the study suggests that "politically motivated unfriending is a new kind of political gesture".
Using the Israel–Gaza conflict of 2014 as its politically-heated case study, the researchers found that unfriending amongst the study's 1,103 participants "was more prevalent among more ideologically extreme and more politically active Facebook users". A total of 16 per cent of users unfriended or unfollowed a Facebook friend during the fighting.
"People unfriend people who have different political views to theirs," co-author Nicholas John told PsyPost. "We already know that Facebook and search engines provide us with a feed and search results that are tailored to us. By unfriending we are further contributing to the formation of echo chambers and filter bubbles. More than that, these findings suggest that the people most likely to unfriend are younger, more politically active, more active on Facebook, have lots of Facebook friends, and have more extreme political views — these are important people in online discussions."
So, rather than helping us encounter a diverse range of opinions with which to challenge our world views, it appears that Facebook is actually a network of closed-minded users who baulk at the first sign of difference.
See how many of them you can get to unfriend you by posting this article on your timeline. We dare you.