The privacy concern here is that because you no longer have to explicitly opt-in to share an item, you may accidentally share a page or an event that you did not intend others to see.
The advice is to log out of Facebook. But logging out of Facebook only de-authorizes your browser from the web application. A number of cookies (including your account number) are still sent along to all requests to facebook.com. Even if you are logged out, Facebook still knows and can track every page you visit. The only solution is to delete every Facebook cookie in your browser, or to use a separate browser for Facebook interactions.
Subsequent requests to Facebook as a signed-out user still send nine different cookies, including your account number, to Facebook or to any page that interfaces with Facebook.