What makes me go nuts though is stuff disappearing from my FB wall (using mbasic web). Lately I see that a lot: see a few interesting entries on timeline, I click one, come back to the wall and they've disappeared and some random stuff from 3 days ago took their place and I can't find them again.
Same happens in YouTube Android app. See a few interesting videos, click one (I can't "open in new tab" in the app...), go back, they're gone and replaced with something totally unrelated. Ugh.
I hypothesized about other benefits and drawbacks here [1].
For awhile you could switch back every time you logged in, manually, to a chronological news feed.
Instagram was one of the last holdouts but they switched a year or two ago.
Twitter is amazingly bad at this. It takes screenfuls of junk on mobile to get to the chronological stuff.
You won't see many of the older posts, and facebook gives no indication that they have been pruned. It's very hard to find old things without just scrolling through chronologically, which is slow and error prone.
Drives me insane.
Hamburger menu > Scroll way down to the "Feeds" section > "Most Recent"
FWIW I would like that option as well.