I ran across this yoga mat recently and I think it would be a great idea for a home mat. When doing yoga on a standard mat which is typically 24 inches wide, certain yoga poses exceed the width of the mat. Now, I am not opposed to doing yoga without a mat and certainly I have chronicled my previous adventures as a mat-less yogi in my post Mat-titudes.
The problem with being partially on and partially off a yoga mat is one of comfort and balance. If for example I want to do a spread leg seated forward bend I would need to turn sideways on my mat and even then the surface of the mat would not be wide enough to keep all of my leg on the mat. I especially notice this in the winter when part of me is on the oh so comfortable mat and part of me travels onto the cold as ice floor. In summer it is not a problem of cold, but rather the unfortunate way my skin clings to the floor when the weather is hot and damp.
Another form of yoga that would welcome this square mat are partnered forms. Sure you can put two mats close together, but there are times that this can allow the mats to slip. Having a single mat for two people would be ideal.
So, to give you a consistent surface to do your yoga no matter the pose, or to allow partnered yoga, these mats are ideal.