Suze Orman's Managing Debt article about Credit Card Companies Boosting Your Rate is about the universal default clause that many credit card companies are using as an excuse to raise interest rates on even their best customers.

The way this universal default clause reads that if they have reason to believe you might become a higher risk, they can raise your interest rate to the maximum allowed, causing your 0% credit card balance to start racking up 20% interest because you were a day late on your cable bill. Credit card companies have monitoring mechanisms in place to monitor all of your bills, not just how you pay them. If you are a day late or miss a payment on a utility, they are using it as an excuse to raise your rate, which increases your monthly payments dramatically if all of your credit cards do it.

Right now, it is perfectly legal for them to monitor your bill paying habits on all of your bills and raise your rates. The best protection is set up automatic bill paying on all bills so they are paid a few days before due. This can save you a lot of credit card interest.