Is TLB a 'Trojan Horse' or 'why are we being tracked by Facebook, Twitter et al?

That's called targeted advertising.

It's cant read other sites cookies but it does read your browsing history and search terms etc and give you an advert based on it. So if it sees your misses going to very every night it knows to give her adverts based on very. Some are cleverer than that and can read the urls you go to and see that it's women's skirts for example and send you very ads for skirts.

Clever, if a little unnerving!

 

I don't use Google at all for this reason, I use a non-tracking search engine.