It isn’t a good idea to surf the web with facebook, gmail (google+), ebay or a lot of other sites “logged in”.
Your “facebook” profile is linked to articles of you like or comment on a news item, ebay ads on other sites are now displaying specific items that you once looked at on ebay’s site saying “there’s still time for you to buy this!” (paraphrased), etc.
You are being tracked and your interests logged. You are being market profiled. And as they say, it’s being done (in part) to focus their sales pitch on YOU as a consumer (imagine a political ad that sells a candidate’s positions one way for some users and differently for another user).
Privacy went out the window in the 1980s when telemarketers and junkmailers got Congress to permit the sale of your private information. That file on you keeps getting bigger and bigger and bigger.
Makes asking for your “mother’s maiden name” on financial transactions a bit worthless seeing as how everyone has that in your file as well.
Just make sure everything you put on Facebook is complete BS.