"“Facebook does massive surveillance. If there is a ‘like’ button in a page, Facebook knows who visited that page. And it can get IP address of the computer visiting the page even if the person is not a Facebook user. So you visit several pages that have ‘like’ button and Facebook knows that you visited all of those, even if it doesn’t really know who you are,” he said."
Jeigu tinklapyje yra "Like" mygtukas, feisbukas žino, kas apsilankė tame puslapyje.