By the logic of "standard rules of thumb" for screen size, most movie theatre screens would be about 10% of the size they are. Now that we have 1080p resolution, you can sit closer to screens and not see individual lines of resolution. If I want to emulate a theatre experience, I want a screen that engages most of my field of vision. That means bigger.

Two other points:

--If you den is 38 feet long, you're either filthy rich or you have a room that's longer than most houses are.

--If you apply your "standard rule of thumb" to a normal-sized room, say, 12 feet...you'd be buying a 24" set.