In the process of working on a chapter of my e-book covering interior composition I came across a couple of shots of a little condo we sold last year that nicely illustrates the pros and cons of a three wall shot compared to a two wall shot.
The upper shot on the right, is effectively a two wall shot and the bottom photo is a three wall shot of the same room. The two wall shot was one of the photos we used to market this home. I liked it the best of the 4 or 5 shots I took of this little living room and the stager, the agent, and the home owner all agreed with my choice. At the time I didn't think about why we all liked the two wall shot the best.
After seeing a discussion in the PFRE flickr group on this subject I realized why the two wall shot feels more spacious and is visually more pleasing.
As you shoot interiors it's important to think about composition and how your decisions about where to shoot from affect the end result.
One of these composition decisions is whether to use 2 or 3 wall composition. The two shots of the same room to the right are an example. Here are some key differences between a 3-wall shot and a 2-wall shot:
As Jeremy Esland explains in the PFRE flickr discussion on this subject, "as photographers, as long as we are aware of the potential effects, we are, of course, free to ignore them, compensate for them or even make use of them."
So you can use a three wall shot to illustrate how large a room is but if you are not careful there can be some down sides of showing three walls.
Here is a very old discussion (9 years ago) from the PFRE Flickr group that discusses 2-wall vs 3-wall composition. I think this discussion gives a lot of great insights on this subject!