Might also be a cultural thing - the Wikipedia articles gives me the impression it was more known in the US than in Europe. There's only one non-English version of the article.
It might be cultural, but the other person who hadn't heard of it is American, and only about 15 years younger than I am.
http://www.nytimes.com/2016/01/17/magazine/the-happiness-code.html
Long. Mostly quite positive, though does spend a little while rolling its eyes at the Eliezer/MIRI connection and the craziness of taking things like cryonics and polyamory seriously.