The article mentions the tracking cookie only works on sites that run the facebok plug-ins. The 'like' button and things.
This is most of the websites on the net including popular porn sites and things.
This site is one of the few sites I go on that doesn't have the annoying like button popping up everywhere. Thankfully Rob is apparently on the side of more rather than less privacy.
The tracking cookie idea doesn't really make sense as far as the friend suggestion list that Facebook generates. After all, how many people do you think visit any given website that you visit? All of them combined? Millions of people if you count up all the people at every website you have also visited just in one day. The friend suggestion list is generated from a closer relationship between two people than just whether you've been to the same website.