How far do I sit from my HDTV screen?

Jim asks, Where did you come up with that crazy formula for viewing distance? I have a 60 inch TV and enjoy baseball and football at 8 feet from the screen. It’s better than being there in person.
This question refers to the HDTV reference I made in my holiday wishlist.
There are a number of different formulas for calculating the appropriate distance to sit from a screen. I mixed the formula for standard def big screen viewing distance with the high definition viewing distance which is based on screen height rather than diagonal size of the screen. Recommendations often vary by manufacturer, screen type, and astrological sign. Ultimately how far you sit from the screen is a matter of personal preference, but 2.5xH (where H is the height of the screen in inches) is a good minimum distance to make sure you have enough room in the space you want to make your home theater.
From a variety of research sources, companies and experts consistently recommend viewing HD screens within a range of 2.5 screen heights to 3.3 screen heights from the viewing surface. If you plan to shop at the local electronics store, measure your viewing area ahead of time so you can ballpark the screen size you want to buy before you get there. You may think a mammoth 65″ screen looks fabulous on the display floor, but fitting it between the windows in the family room or finding a room with enough viewing distance in a house built before 1970 might be a challenge.
According to a formula that was previously published on the Hitachi support website, you should sit 3.3 times the height of the screen for a “best visual experience.” Their quick-and-dirty in store measurement is to double the diagonal for a rough estimate of distance. Here they contradict themselves a little, because their published distances and the distance of 2 times diagonal are distances that vary by more than 12 inches.

Hitachi Numbers vs. Two Times Diagonal

Screen Size 3.3xH 2xDiagonal
65″ 106″ 130″
57″ 93″ 114″
53″ 86″ 106″
51″ 83″ 102″
43″ 70″ 86″

Richard Fisher of HDTV magazine offers a different take on what he calls Critical Viewing Distance. Fisher presents critical viewing distance as a range falling between 2.5 and 3.3 times the screen height. This falls directly in line with most other sources on the subject and leaves some room for personal preference to be a factor in the decision making process. The theory being anything closer than 2.5 times screen height makes digital artifacts and other imperfections in the image more apparent. Outside 3.3 times screen height, you might as well save some money and get an enhanced definition screen or standard definition big screen because you aren’t taking advantage of the improved picture.
Based on these numbers, the critical viewing distance for the same Hitachi screen sizes listed in the above example break down as follows:

Screen Size Screen Height 3.3xH 2xDiagonal
65″ 32″ 80″ 106″
57″ 28″ 70″ 92″
53″ 26″ 65″ 86″
51″ 25″ 62.5″ 83″
43″ 21″ 52.5″ 69″