Sharing with friends
If you have the square footage and budget to support it, I cannot emphasize enough the benefits of having more than one cat in the house. I say this not so much for your enjoyment (although there's that advantage as well), but for your cat's sanity while you are away. While it took a little time for our two cats to accept each other, they now are more than happy to share prime sleeping spaces.
Problems can arise when a cat lives alone and is bored. Many spend too much time at the food bowl...others can become destructive towards furniture...it's even possible for a cat to get aggressive towards people if they don't have a healthy outlet for exercise and play. No matter how much time I may spend with my cat, my home pales in comparison to their natural habitat where a cat's exquisite senses are stimulated to the max. Toys can be a great supplement when you are out of the house, especially if you keep a rotation that upholds each ones novelty. However, a feline companion is the best toy of them all - unpredictable, engaging and creative.