Now, I am quite confident I have not uttered word "Piketty" anywhere else in any way (not from my mouth nor keyboard) in a long time. But now my Facebook feed i

Now, I am quite confident I have not uttered word "Piketty" anywhere else in any way (not from my mouth nor keyboard) in a long time. But now my Facebook feed is filled with advertisements to buy piketty's book. If this is not an anecdote, how do they do that?