Funny. I thought so some couple of days ago too. I think something similar happened to me when I had it in mind to purchase a red tie for my sunday outfit and on logging to Facebook, I saw an ads on where to buy 'my desired color' of ties. Facebook truely is fast becoming too intrusive. I hate it sometimes.
It definitely is disconcerting. I've heard that some people actually like it - like Facebook is their friend by personalizing their experience. Very strange...