Anecdote time... So, I was sitting in a car with a colleague who was talking about how he used to live in the UK (we're both Danish but were speaking English because we had a non-Danish colleague in the car with us). My colleague talked about how he'd developed a fondness for cricket while living in the UK, to which I replied that I only really knew cricket from Hitch Hiker's Guide to the Galaxy and that it was one of those sports that I'd always been sort of curious about since it gets so little exposure here in Denmark. We agreed that we should maybe watch a game together so he could explain it to me and the conversation naturally changed topic shortly after. But a couple of days later Google Now showed me a notification saying that cricket results were available asking if I wanted to subscribe.

There's of course always a chance that I've done something that—unbeknownst to me—has led Google to believe I was interested in cricket, but I definitely didn't google "cricket", watch videos about it, mentioned it in emails or some such.