How Big is Too Big?

You can calculate THX recommended screen sizes here. The recommended screen size for a given viewing distance is often a lot bigger than you might think.

I started with 42", then 50", now 60". Bigger is often better, and it's not just Freudian. Having said that, strictly following the THX guidelines can result, IME, in a screen size/viewing distance that allows you to see the limits of the image's resolution (i.e. pixels), which I find very distracting. So you have to let your eyes make the final judgment.

Cw - I agree that most people sit much farther from their screens than the THX guidelines recommend. I sit at 9 feet from a 60" screen, so I too am farther away than the guidelines, but probably closer than most viewers.

I find the distance at which I can start to see pixilation, then move back a couple feet. That maximizes the impact of the screen's size while not allowing me to see the limits of the image's resolution.

Of course, the higher the source resolution, the closer you can sit without seeing the limits of the image's resolution. This may explain why people sit so far from their screens - they developed their habits with low resolution images, which require farther viewing distances to avoid seeing the limits of the image's resolution, and they have not adjusted their habits as high resolution sources have become more common.