How big is too big?

There has to be some sort of ratio of room size to screen size. I was thinking about getting an 84" screen but realized that it would be WAY TO BIG for the room after drawing it on the wall with chalk. Have any of you put too large of a TV in a too small room, or the other way around?
It's not necessarily the size of the room that comes into play, it's the viewing distance that you have to worry about. The other thing is "physical size". Will it fit into the room without dominating it ? With that in mind, look for a TV that can be viewed at "off" angles and at various seating heights. Most bigscreens fail miserably at this test. I can watch my 55" from 18 foot away at a 90* angle in another room looking over my shoulder with NO problems or distortion whatsoever. This comes in handy when my girlfriend is watching something that i find "half interesting" and i'm playing on the puter. Like now : ) Sean
I have a 60" and recently moved to a place with a smaller room. I am about ten feet away and its to close. I dont like to have to turn my head to see the whole screen. I would measure how far your seat is fron the tv and then stand that far away from the tv's you are looking at.
Hi Tireguy. I'm 12' feet away from a 55" and it's just fine. "How big is too big"? Open ended question. Like "Sweet Dick Willie" said in "Do The Right Thing"... "it's never too hot to #%&*". And, there's no such thing as "too big" when it comes to TV (or audio, for that matter). Just gots to move stuff around ;-)
If you're not buying HDTV, audition the TVs from your expected viewing distance as Perfectimage stated. Buy the biggest screen where you can NOT see the horizontal lines. From 10-12 feet away you'll likely end up with a screen size 50-60 inches (I use 50 inch from 11 feet). If you're going HDTV, then the audition is that much more important because it will really be a comfort factor vs. performance. Hope this helps.
For a rear projection tv the ideal seating distance would be 5x the viewable screen height. For example if you own a 50in RPTV and the viewable screen height is 30in, than your ideal seating distance would be 5x30 or 150in or 12ft - 6in. After this advice read Sean's post.
The other key issue is how big a wall you need for everything that has to be up front. In addition to a screen, you have to accomodate speakers, including possibly a sub. To have a 55" screen with adequate placement of speakers, etc. you probably need on the order of a 12' uninterrupted wall, which isn't always easy to accomodate.
As many have pointed out it's the viewing distance that matters, but it also has to be coupled with projected resolution. When I watch a movie I don't want to see scan lines. If you project too large and you are too close you will see those lines. Other than that--the bigger the better in my opinion. Does anyone think IMAX screens are too big for the theater? SGTH did an article on this (distance vs resolution) quite a long time ago, it might be possible to find it in the archives. Just as a point of reference I'm using a 100 inch screen, seated 15 feet away, native resolution is 800x600 (CRT driven with Faroudja DVP220). Hope this helps.
Thanks for all of the help I just got a 100in front projection screen, and I think I might have been able to fit a 120in. Very overwhelming just what I wanted heh heh heh.
NTSC stated that screen size V. viewing distance should be calculated by diagonal size times 7 feet to eliminate the scan lines. I often hear people complain that their TV looks grainy, they are simply sitting too close. Don't let ego or oneupmanship play a role in your TV. Leave that to your true audio dealings, you'll be happier!