And what it turned out was going on was that Facebook was looking at which links I clicked on, and it was noticing that, actually, I was clicking more on my liberal friends' links than on my conservative friends' links.
Och visade sig att Facebook tittade på vilka länkar jag klickade på och siten noterade i själva verket, att jag klickade mer på min liberala vänners länkar än på mina konservativa vänners länkar.