Ask anyone - a vet, a supposed "cat lover," or even a random person on the street and they'll tell you that the cat's tail is what gives it the balance to crawl in high, narrow spaces. I'm sorry, but that's just not true.
Cat Fanciers Association uses the following as a description for our little extra terrestrials:
This elegant cat gracefully glides across the room on its tall, slender legs.
Now, if any of the members of the CFA actually owned a cat, the description would be more like:
This elongatedly furball waddles over to the foodbowl, but decides to plop down first and have a 20 minute bath in the middle of the living room while you're trying to do housework.
There's very little about the common cat that can be associated with grace and poise. At this very moment, there's about a pound of meow mix scattered all over the kitchen floor because someone crashed into it while running around. There have been many mornings where I've come downstairs to find dining room chairs tipped over or curtains lying in a heap. Further evidence can be found here.
The tail, I believe, has a useful purpose in the lives of cats, even if it isn't for balance. Much like an antenna on an old-fashioned cellphones (or, and we're going way back here, on televisions), cats use their tails for easier communication with the mothership. An erect tail can mean many things, from being frightened or being happy to see you, but it can also mean that the cat is transmitting messages to and from space.