Stallman: Facebook IS Mass Surveillance

“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.