It's called Dunbar's number, and I agree all social media platforms should have that limitation by default. Once you reach that number, all the rest should be followers (if you agree to allow them to follow you).

https://en.wikipedia.org/wiki/Dunbar%27s_number

So you're saying there /are/ things that the social sciences can contribute to data science? This is my complete lack of surprise...

There was a social network based on this premise, Path:

http://observer.com/2011/09/the-path-to-dunbars-number-and-y...

Apparently still extant, though it failed to take the world by storm.

https://en.wikipedia.org/wiki/Path_(social_network)

Its initial experience is underwhelming.

https://path.com/login

This is a good idea for a platform specifically for close friends.

The Path social network did just that. Originally 50. Then 150 and now I believe 500.

"I'm sorry, Jeff, you know I like you. I enjoy our chats, we had a great time at the game last week. I love your stories, and we are definitely on for Venezuela. I just have a lot of other friends and you just didn't make the cut."

"You called me out to lunch to tell me this?"

"No - I need you to tell Katie and Tom that they're out too, and maybe see if you can get an email address from them. I don't have any other contact for them."

"... Fuck Katie and Tom. And fuck you. Pass the syrup."

"Sorry. It's nothing personal..."

"You know you're down around #140-150 on my list too."

"Jeff I see you only have 37 friends on here. Why do you think you're out? You're making me look bad."

"You know fuck you. At least those other 36 people are ones I can count on. They're the ones who will be at my wedding"

"Actually you can't make events until you have 50 friends."

"What the fuck!!"

"Sorry. Oh. Look on the bright side, Jeff, it says your fiancee just unfriended you. You can always try living as a hermit, it's like your natural talent."

Sounds a the Black Mirror episode. Actually the one about the social ranking system

LRU

Doesn't work. Simply because of nth order effects. This type of reductionist approach cannot be plugged-in by design. Simple solutions grow out of complicated ones following some evolution not the other way around. The proof is they kept moving the number upwards.

This could be mitigated by just having people you don't interact with often in some meaningful way (for some definition of meaningful), they just get automatically unfriended. As if you had forgotten about them.

There's not hard cut _per se_, just that after the 150th, if both people don't interact, the relationship fades away...