Mashable published an article by Christine Erickson today on whether small businesses should automatically follow back on Twitter. The article and comments just cover the extreme positions, automatically following everyone or manual follower management.
Some companies can get away with not following anyone, or maybe just following related accounts, but in most cases a business wants to engage with their followers.
Catfood Follower provides a third way thanks to integration with Klout. You can automatically follow anyone with a high enough Klout score. This helps weed spam and bots out of your stream (and following list) while ensuring that you follow authentic and influential accounts.