Netflix are very very sensitive to this problem because it's much harder for them to sell against their biggest competitor (local cable) since they rely on the cable to deliver their service. If the service goes down, then the cable company can jump in and say, "You'll never lose the signal on our network" -- blatantly untrue, but it doesn't matter.
When you're disrupting a market, remember that what seem trivial is in fact hugely important when you're fighting huge well-established competition :)
I have not had a single service issue with them, ever. They do a better job at reliably providing me with TV shows than the cable company does. That seems to be where they're looking to position themselves, and the reputation for always being there is hard to regain if you lose it.
This is even more true if/when you load balance between zones and aren't just using them as hot backups. As another commenter pointed out, Netflix says they have three zones and only need two to operate.