This question popped back onto the main screen recently:
Why did Facebook not use HSTS for a long time after it became available?
Both the question and all answers are now incorrect, because Facebook now use HSTS. I'm not sure when they started doing so.
I have edited my answer to include a warning, but I wonder: how do we want to deal with this? Some questions have been closed because the answers would be too transient, but that seems a shame, as I think the question was interesting and useful at the time.