So do you de-friend people if you get a job with them? Or do you regard people you add after you've finished working with them as 'real Facebook friends' and let them stay privy to your social life?
I know I've definitely experienced a bit of a 'chilling effect' on the stuff I post since adding a few former colleagues. Tech is a small town and you never know who you'll be working with next year.
Someone who is your friend and then becomes your coworker is still your friend.
Someone who is your coworker and then becomes your friend is likely not really your friend in any real sense, unless-and-until you leave that job and they bother to remain in contact with you.
It's not a question of following some flowchart; it's a question of whether a given person values your relationship with them more, or values how they could get ahead using the information they've learned about you more. This fact is generally illegible for current coworkers, but mostly resolves out once you leave that job—the people who valued you personally keep in touch.
This fact is also generally legible for people who you meet outside of work: people mostly don't bother to get to know you unless they [expect to] value you personally. (Or they're conducting some form of long-term industrial espionage. I don't envy the people important enough to worry about this.)
I know I've definitely experienced a bit of a 'chilling effect' on the stuff I post since adding a few former colleagues. Tech is a small town and you never know who you'll be working with next year.