If your ISP is not an OC partner you mostly get connected to some server dynamically leased from Limelight's, Level 3's or Akamai's commercial CDNs. They largely have no control over the route your traffic from and to those servers take through the Internet or the congestion on that path or whether those paths cross networks which are intentionally throttling Netflix traffic.
Whoever is to fault for that, I can tell you one thing that is Hasting's fault: to have those stupid 240 and 384p encodes. Any stream should start at 480p, period.
This much I can agree with. Most titles have 320x240 (235 Kbps) , 384x288 (375 Kbps) and two 512x384 (560- and 750 Kbps). If your network service speed is insufficient to keep ahead of the 1050 Kbps 640x480 stream you should give up on streaming video and find something else to do.
Besides, Netflix should respect the choice of the user. In the account settings you have a choice of four qualities, low, medium, high and auto. Well, if I set it to high, why the hell do I get an "auto"? If I set it to high, I should see a buffering bar until my player is able to show me a 5.8 Mbps stream, period. If you are the kind of person that cannot wait, very well, set your account to "Auto" and you'll get the crap that we all currently get. But the user should have a choice.
Those setting were to throttle the maximum amount of bandwidth which would be used by your streaming, not to designate the minimum. They were added because some Canadian ISPs were imposing truly draconian bandwidth caps on their customers. "Auto" is a very recent addition; I have absolutely no idea what is meant by it. (If you look at Netflix's support page on the topic all of the first three settings specify "up to" a certain amount of data per hour, whereas "Auto" says "adjusts itself automatically to deliver the highest possible quality, based on your current internet connection speed"; other than there not being a limit I don't know how that differs from the others. Those limits should be reviewed and revised.
Unless your device can buffer an entire film, which extremely few devices have the storage for, if the bandwidth you're getting on your paths to Netflix servers is insufficient to keep ahead of the chosen video encode bit rate the buffer will slowly empty and the player will have to stop and refill over and over, at a rate which is slower than realtime in the content (if you're only getting enough bandwidth for a 1750 Kbps encode it will take over 3 minutes to buffer 1 minute worth of the 5800 Kbps one).