[Tichy]

Of course they do. To the maximum extent they can manage. As the saying goes: if you are using a web service for free, you are not their customer, you are their product (or something like that).

[icebraining]

Paying is irrelevant. How many websites hide the FB buttons if you subscribe to them?

[Tichy]

I meant you don't pay for Facebook. Facebook is collecting the data, not the sites who add the Like button.