Like I said, I kind of expect companies to do this. It's probably a lower competition key word, and the forum still even today gets decent traffic. Not as much as "Bitcoin Reddit" I bet.
It might appear unethical to members here but it is not illegal. Their advertising team must have coordinated well with the legal team before deciding keywords.
I suppose, but the advertising industry hasn't got the best reputation for ethics. Especially, certain industries. Although, I don't think they're doing too much harm. They're just trying to generate more revenue, and Bitcointalk as a keyword will have less competition. Although, I'd have thought they've got enough money to compete on the more popular keywords too.
I haven't seen it on other devices.
So far I've only seen it on a device that I search for "bitcointalk" in anonymous browser mode, that is, it doesn't even keep browsing history. And what's also strange is that it only appears once. That is, when I repeat the search it does not appear again.
I haven't used Google's search engine in a very long time now, but don't they sort of cycle through a bunch of adverts, so even if you did refresh it might not be the same advert displayed? That's usually, how adverts work across the board, I just can't remember how Google does it. So, you could just get unlucky, and not see that advert for a while, but they're still paying for it.
Does it get replaced by another advert when it's not there?