Just one issue that may come up…
If someone is “friends” who may not be as makpid on snius or negiah as they should be, their pictures come up on your feed and you see their pictures. Even if they are the same gender as you, everyone in their pictures may not be, and it can be a serious taiva that’s best avoided.
Sometimes it is not so simple to just delete that person because then you may need to explain why, and not everyone is so understanding either.