"full opt-out" in the title is very misleading. They are disabling the mini-feed and newsfeed stories only! FB still gets the info on your browsing/buying habits by default, unless you would click the link to not share the info with facebook every time you make a purchase.
From the article: "If you select that you don't want to share some Beacon actions or if you turn off Beacon, then Facebook won't store those actions even when partners send them to Facebook."