That weird phenomena of talking about stuff then getting adverts, while I absolutely despise all advertising agencies and wouldn’t be surprised if it is worse, I reckon is down to other people who were also exposed to whatever webpage it was that made you think/speak about it who then go on to search it in Google, and therefore your profile gets some likelihood associated with it that you’d be interested in that too and worth an advert.

That doesn't account for the times that it's something that's entirely offline that makes you say it.