I really dislike this option. It means that material I posted here, thinking it was going to my Christian on-line friends, would be visible to all kinds of other people. I have a distinctive writing style that a lot of people recognize, and they do not need to know my prayer requests, nor my politics or theology.
Because even if you post someone else's post, they can come and look at what I posted. Strangely enough, I find there are many coincidences in life. The internet is a small place, relatively speaking, and it is amazing how often things can be linked.
There is nothing I am particularly embarrassed about in my posts, but I would like them to remain where I posted them, not linked and posted to FB or Twitter, and then linked again and again. I know this forum is public, and if people come here and read my posts, that is one thing. But to have them moved to another place, I would have to completely object to that invasion of my privacy.