I would have said at first Mark Zuckerberg should make a public apology to hurting facebook users but apparently he has finally done that in a newspaper ad after intentionally avoiding it and trying to bring some logic out of it. This is just the beginning of the path to regaining users' trust.
Users should feel totally secure to share their private information with those and only those they have decided to add as friends without fears of having sensitive data about them leaked. What if there's a breach or hack like that of iCloud few years ago? That left many users including celebrities feeling insecure as their "private" and "deleted" photos and more were leaked.
I think they should make all user data less accessible without the user's content. There should also be a tool in the news feed to see all third-party apps with access to member data and an option to easily block any unwanted access.