This is a good point, Facebook has 1 part of the puzzle, Google has the other. Facebook knows "who you are" better than Goog, Goog knows that you want "right now" better than FB.
I think that Google probably knows who you are pretty well. How often do you log into Gmail and then forget to log out and do searches on Google? Even without doing that, it's still tracking you via cookies.
You're fooling yourself if you don't think that Google has been tracking you and your searches for the last ten years.
In fact, I would guess that it knows a fair amount of things about you that you would never post on Facebook.
What if you also know that the person who's googling for "Ford Focus" is of driving age? Like, uh, Facebook does.