@browncoat - The whole point of a credit card, from the company's view, is for you to spend more on it, so they can charge you more fees and interest.
And the interest rates are often really big. Even the best credit cards are usually around 15% interest.
On the other hand you need a credit card so you can show that you are a responsible person and build up a good credit rating. I've known some people who managed to get an $8000 limit and immediately began spending on it. Money they would never be able to afford to pay back even without the enormous interest charges.
It's much safer to keep to the minimum credit card limit.