If you think this is alarming: Facebook also collects what you decide not to post, tech consultant warns – Technology & Science – CBC News, then I have more news for you.
Not only can Facebook do this, but they can do other things. For example, if they wanted to, they could track where you move your mouse, even if you don’t click on something, using technology like the kind mentioned here: web page mouse tracking – Google Search.
In fact, you don’t even have to go to Facebook to have them track you: Facebook Is Tracking Your Every Move on the Web; Here’s How to Stop It.
And if you use Facebook on your mobile phone, there’s potentially even more information they can track about you.
So, lots of reasons to be concerned. I all but avoid Facebook, but it is not an easy thing to do. In addition, I don’t think Facebook is the only one that does this. They seem to be just the most notorious.