While I agree with what gstarr says in general, there is one thing that I would perhaps disagree with. That is the issue of the affordability of having a large collection of HD movies.
Now ripping Blu-ray discs can consume up to 30 GB which would make what gstarr says seem correct. A 1 TB drive would get used up pretty fast. But there is a lot of extra space consumed that is not really necessary for many people by ripping the files to the computerdisk, not to mention this is probably illegal these days.
But there is another method of making a HD movie collection and that is to collect movies encoded at lower bit rates than Blu-ray will provide but high enough to rival OTA broadcasts. I use 9 mbps for most of my movies with h.264 compression and they run about 6-7 GB per 2 hour movie. That's about 150 movies on a TB drive. To me that is very affordable.
Now I'm sure the question of where do these file come from is bound to be next. I get them from my U-verse DVR that I play into a Hauppague 1212 HD PVR box attached to one of my HTPCs. I also will use another HTPC that has a combo HD DVD/Blu-ray drive to play into the 1212. Sometimes if there is a good version from broadcast TV, I will use the captured file from my MIT tuner and strip the commercials.
So far I have collected about 200 HD movies, many of which are not available on Blu-ray.
For more info on the 1212 see: http://www.highdefinitionblog.com/?page_id=331