Most everybody with extra large screens and freedom to sit anywhere they want end up sitting between 1 and 2 screen widths away from the screen, depending on individual preference.
That definitely holds true for projection screens, but smaller TV screens people tend to want to sit further away. I thoroughly enjoy a 1:1 seating ratio for my regular projection viewing - I have a 120" projection screen (9 foot width) and my front row sofa seating puts the viewer's eyes at just under 9 feet from the screen. But for 3D movies, I like to move the sofa another foot or two closer!
FEEL an awesome 3D Blu-ray movie in the Frey Theater - Now with projection in glorious "FREYMAX" 3D!