When expectations are high, if expectations aren't met, the adjustment can be abrupt.
Time Warner (HBO + Warner Brothers + numerous cable channels) is in the same content/TV distribution business, $4.3b in profit, market cap of $62b.
Netflix, $0.2b in profit, $5b in REVENUE, market cap of $27b (well, now $20b).
Netflix is competing with Amazon streaming, Apple TV/iTunes, to a lesser extent Google, Hulu.
Also now HBO, they announced today they would start letting people subscribe over the Internet without a cable subscription, all the other channels are getting in the over-the-top streaming business.
Comcast + Time Warner Cable (different from Time Warner) are looking to merge and perform a cashectomy on Netflix via 'fast lanes', before TV subscriber losses from cord-cutting really start cutting into their flesh. (Can anyone doubt that's about to happen? Anyone who has compared the experience of e.g. Roku with a cable box can see over-the-top is a 10x improvement in UX at a lower price. And with even HBO available over-the-top, literally the only reason left to subscribe to cable is live sports.)
Growth is not a given. It's a tough landscape and no guarantee Netflix will be the last one standing.
$20b is still a lot of money for a company with no profits, in a fight for its life.