If you've ever sat on a train or a bus and the person next to you keeps reading the messages on your phone as you send and receive them, then you'll know how annoying and rude it is.
But imagine if that nosy strange was actually your mother-in-law, who insisted on always going through your other half's phone.
You're probably think you'd get your partner to make sure it was always locked with a password your mother-in-law couldn't guess, but if you didn't do that, or she always managed to work it out, then one guy has - allegedly - come up with a surefire way of stopping that from ever happening again.
On a thread on Reddit, one husband described how he exacted his revenge on his snooping mother-in-law.
"So I'm married to a wonderful woman," he wrote. "She's smart, funny and very kind."
He then went on to describe his mother-in-law in a warm, pleasing light: "Her mother is generally very nice and tends to have a great attitude and be very enjoyable, a bit of a prude but generally enjoyable."
As well as a bit of a prude, he writes that she 'can be a bit of a major snoop'.
"If my wife leaves her phone sitting around she will just pick it up and start going through it. My wife has kind of laughed this off as a remnant of her mom being controlling when she was a kid," he said.
Which is probably where changing the password - or putting one on the phone - should come in. Because, as he admits, it's none of her business.
"I'm not a fan of this because my wife and I will sometimes text about thing that simply don't involve her mother and I don't feel are her business at all."
Instead of making sure his mother-in-law couldn't access the phone, he devised a plan to make sure she'd never want to pry into her daughter's phone again.
"Over Christmas my I saw my wife set her phone down on the kitchen counter and I had a brilliant idea," he wrote.
"Her mom was still in the kitchen and I sent my wife the most sexually depraved text about all the things I was going to do to her when everyone left. (Honestly most of them are things we haven't even done, but I had to make it extra scarring ...)
"I sent this text from the bathroom. And maybe it was my imagination but I could swear I could hear an audible gasp shortly after her phone went off."
If the gasp wasn't enough to know his mother-in-law had read his text, the fact she couldn't even look at him gave the game away.
"When I went out her mother absolutely would not look me in the eye. Then not-so-discreetly asked her daughter to come talk to her in the other room.
"When my wife came back into the living room I thought she had been crying, however upon closer inspection she was laughing.
"Her mother had questioned her about me...and if I always talk down to her like that.
"My wife had told her kindly that what we do is between us and us only.
"Probably the best gift this Christmas."
It must have been a bit awkward passing the parsnips around after that. Still, changing the password probably would have avoided the years of bitterness that will undoubtedly follow. You win some, you lose some.