Samsung makes phones that compete with Apple, yet is also one of their biggest suppliers. This happens in business all the time.

AWS knows that if they did anything to harm Netflix's business, it would reflect very poorly on them (and be morally and ethically wrong).

Also, while both offer streaming services, they don't really compete. Many people subscribe to both services.

What you said is true, but Samsung and Apple do have frictions, and I believe both of them do have contingency plans that hedge against the risk of a full out war between them. What amazes me is Netflix's seemingly "un-conditional trust" on Amazon, it seems putting them in a potentially very vulnerable position, even without considering Amazon Video being a potential competitor. Maybe they just don't have any other choice right now.

Along the same line of questioning what's to stop Netflix from packing up bags and moving to GCE/Azure?

Cost. Switching would cost a ton of time and money, which is probably better spent in securing streaming rights for popular shows, creating their own shows, and marketing to increase their subscriber base.

Netflix is a high profile enough customer that I think they would get amazing discounts from MS or Google if they moved, just so those providers can parade around talking about this massive high-profile defection.

Agree, switching is so costly, and IMHO given Netflix's current profit margin, which is not that high, I doubt they can afford to replace aws with a full in-house solution.

Lack of features and/or scale.