Netflix's extraordinarily specific micro-categories have become both a running joke and a surprisingly effective recommendation tool, but how does it serve up personalized recommendations for "violent sci-fi thrillers" and "gory action and adventure," and why are "violent" and "gory" separate descriptors? And why, when you reverse-engineer Netflix categories as Ian Bogost and Alexis Madrigal did for The Atlantic, are there 19 genres dedicated to the man who played Perry Mason? By scraping the tens of thousands of possible Netflix categories (most of which users will never see), Bogost and Madrigal put together a strangely effective map of how Hollywood makes movies and how we seek them. And behind it all is Todd Yellin, the Netflix VP who envisioned the tagging system in the first place: "Predicting something is 3.2 stars is kind of fun if you have an engineering sensibility, but it would be more useful to talk about dysfunctional families and viral plagues."