Netflix has succeeded on the strength of two things: integrity and ambition.
They genuinely care about their customers. They work extra hard to make sure people who give them money are happy to do it. In their call centers, CSRs are friendly and empowered. They're instructed to err on the side of doing things that are most likely to make a customer happy, instead of pissing people off with stupid "it's policy!" behavior. In their distribution centers, they have a hardcore quality control culture that goes to great lengths to ensure that mailed out DVD's correctly match a customer's order.
Contrast this with their dying competition, who never once gave a damn about customer satisfaction. Who, indeed, codified policies whose direct result was to enrage customers.
As for ambition, Netflix has continually worked hard to make the service the very best it could be, opening more and more distribution centers to minimize the wait between returning and receiving your DVDs. Despite having every reason to rest on their laurels, they decided they'd also be the Netflix to their Blockbuster, going deep on the Watch Instantly strategy that's redefining their business. Instead of waiting for someone else to come along and make them obsolete, Netflix grabbed the bull by the horns.
This is one of the rare moments of modern capitalism producing something truly excellent, on its merits, based on the needs of the market. If only we could see similar disruption in larger and even more corrupt industries.
Honestly: I love these guys.