If you already have a cat and want to add another cat as a companion, we have lots of cats who enjoy the company of other cats as well as people. (thunderingpaws.org)
Cats who are stressed by the presence of other cats outside the home can be discouraged from watching out windows. (petenrichments.com)
There are also reports of high carbohydrate / high grain cat food causing a number of other cat health problems. (cat-lovers-only.com)