You don't have to type stuff into a Facebook.com input form for them to be able to use it for ad targeting. There are Facebook "share" buttons on most websites, and each of these is a tracking beacon that tells Facebook that User X visited so-and-so website. That X becomes an identifiable user if the user is logged into Facebook on the same browser at the time of the website visit.
You don't have to type stuff into a Facebook.com input form for them to be able to use it for ad targeting. There are Facebook "share" buttons on most websites, and each of these is a tracking beacon that tells Facebook that User X visited so-and-so website. That X becomes an identifiable user if the user is logged into Facebook on the same browser at the time of the website visit.