> You have deals with N big media companies who each have their own restrictions on who can stream what from where. The list is constantly changing, so permissi

> You have deals with N big media companies who each have their own restrictions on who can stream what from where. The list is constantly changing, so permissions to view media are locale-specific and revokable; you need a way to say “okay this person is not allowed any more to do that.” Yeah, international media content licensing is very likely Netflix's moat. I'd wager starting a streaming service, and getting the big studios to host their content is pretty much impossible. Recommender systems are pretty well studied, and anyways, I'm sure it's significance for Netflix is overrated. People (including me) tend to watch the show everyone's talking about. It's a much more hairy issue for a site like Youtube, where users upload decades worth of content every day, and the site has to figure out what to show to which viewers, where the content's shelf-life might be measured in days, so building up collaborative filtering data might not be feasible. All the other technical issues are probably non-trivial, but I don't think any of them requires world-changing engineering prowess. Most engineering is non-trivial. If I attempted to design a washing machine, I'd probably fail miserably, and figuring how to do it well probably took collectively thousands of engineer-years. Doesn't mean it requires exclusively unicorn engineers.