Well, as it turns out, they're probably full of crap.
According to a sexologist and relationship expert, it could be the case that the couples who post the most about their relationship, and share the most selfies, could be the least happy together.
Dr Nikki Goldstein explained in an interview with the Daily Mail that couples who aren't confident or satisfied in their own relationship are more likely to seek validation by sharing selfies etc on social media.
She said: "In my job, I get to see what people post, but I also get to hear what goes on behind the scenes in those same relationships"
"But as I look through my Facebook feed, everybody seems to tell me they're so ecstatically happy."
"Often it's the people who post the most who are seeking validation for their relationship from other people on social media."
Sounds about right to me. If you're so happy, why do you feel the need to rub our noses in it so much?
"The likes and comments can be so validating that when someone is really struggling, that's where they get their up from - not the person making the gesture, but what other people will say about it."
I'm sure we can all think of a few friends who fit this category of social media user. They post a selfie with their partner, along with a mushy status, only to break up a few weeks later and get with someone else.
Dr Goldstein also touched on the theory that the time invested in creating these posts and monitoring their reception could do further damage to a faltering relationship.
She said: "You see people who will focus so much on taking a 'relfie' - a relationship selfie - and getting the right filter and hashtags that they're missing the moment.
"I think, why don't you take a photo because it's a nice memory and a moment you want to look back to?"
Right - I mean, why do you even have to share it?
"Couples are taking these photos, straight away putting them online and then watching the likes and comments instead of being with their partners."
Whether or not we like to admit it, we all do this - making sure enough people have liked, seen, or shared your post. It's pathetic enough as it is, but when you're doing this with your supposedly-intimate relationship, it takes on a whole new dimension of potentially destructive behavior.
Dr Goldstein said posting 'relfies' in itself was not necessarily a bad thing, but couples should guard against overindulgence in this respect.
She said: "Keep it fun and entertaining for people - not mushy and possessive. Nobody wants to see post after post about how in love you are and how amazing this person is.
Dr Goldstein summed her argument up well by saying "The questions to be asking yourself are: are we the same in the real world, away from our screens, and are we more concerned about how the relationship actually is, or are we more interested in how it looks online?"