Dangerous sharing personal information with 3rd sides - everyone who creates an application for FB you use, gets acces to your profile. I'm afraid also from acces of simple view of each profile for everyone - list of friends, fullname and photo is enough to determine one person. Also there are known issues in security of FB, which are not solved.
Je reçois des mails de demande d'inscription de moi-même ou de personnes déjà dans ma liste. Il s'agit donc de spam
Spamming : I receive asking to become friend from myself or people allready in my friends list!
Facebook is continuing to make more and more of your personal information public by default, and is increasing access to it for it's 'business partners' such as Pandora and Microsoft Docs. Be careful of what information you post, especially phone numbers and addresses. In addition, every time you add an 'application' you give that 'app' full access to your information.
Also, that update issue when everyone's settings got defaulted to Public worries me.