I am shocked to hear so many people thinking that this was a secure site in the first place.
If you allow people to know where you are, who you are etc it doesn't serve as protection.
Also, even if you had to become a member to log on and read posts, we already have seen the damage.
And, you can copy and paste posts, print posts , there is even an icon to email posts directly from the site.
So, really, membership isn't going to stop a potential terrorist from this site and sabotage what they want to sabotage.

It is one thing to post how you are dealing with your day, your illness etc. But, when you start totally personalizing your posts, your BIO, your pix then that is where the threat of security breach comes into play.