The Boston area Comcast customers are testing a DVR with no hard drive that stores movies in the cloud and streams them on demand. Tivo is coming out with a semilar device. This is significant. I’m not sure how long it will take to get the bugs out. My best guess is a couple years to reach Portland. My guess is the recorded data goes from some sort of hub and is ” flagged”as being recorded by you. So Comcast stores one original for multiple ( thousands)  of subscribers. When requested, the origiinal is streamed to the requester. I’ll have to work out in my head how this is different from “ON DEMAND”. To recap, the DVR is a database and a fancier streaming center and a fairly cheap box connected to your TV. This is my first guess.