"The biggest complaints we're getting right now are the cards that raise your interest rates for no reason," says Gerri Detweiler, a credit adviser for Credit.com. "They really don't give a reason. Typically, if you talk to them, they will say it is the state of the credit market. They just have to."

And for now, that is perfectly legal. Many issuers include a clause in the fine print reserving the right to raise interest rates based on market conditions.

"I think if I'm in the market (for a card) and there is any chance at all that I'm going to carry a balance -- or even not -- I'm going to find out what is the exact policy of this issuer about jacking my rate up. Most issuers have this kind of a catchall that says that if general market conditions are bad, they can raise your rates," says Curtis Arnold, founder of Cardratings.com and author of "How You Can Profit From Credit Cards."

"I can tell you this: You can't find anyone that would say that general market conditions are favorable right now," he says.

According to a 2008 survey by Consumer Action, not all issuers change terms based on market conditions. But 17 out of 22 issuers surveyed (77 percent) say they can change terms at any time for any reason.

But take heart -- credit card companies can only play this game until July 2010.

Thanks to reforms adopted Dec. 18, 2008, by the Office of Thrift Supervision, the Federal Reserve Board and the National Credit Union Administration, consumers who are less than 30 days late on their bill cannot be dealt an interest rate increase.

Plus, credit card companies will be prohibited from raising interest rates on existing balances.

How to avoid: Shop at local credit unions and smaller banks. Small credit issuers tend to have more consumer-friendly policies, Detweiler says.

Arnold agrees that not all issuers have that catchall phrase in place.

"They tend to be smaller issuers, like Simmons Bank in Arkansas or credit unions," he says. "Check your cardholder agreement and any change in terms carefully. If you can't find anything, call your issuer."

This paragraph from the terms of the Citi Professional Cash Card illustrates how credit terms can change because of forces within and outside of your control.

Rates, fees, and terms may change: We have the right to change the rates, fees, and terms at any time, for any reason, in accordance with the card member agreement and applicable law. These reasons may be based on information in your credit report, such as your failure to make payments to another creditor when due, amounts owed to other creditors, the number of credit accounts outstanding, or the number of credit inquiries. These reasons may also include competitive or market-related factors. If we make a change for any of these reasons, you will receive advance notice and a right to opt out in accordance with applicable law.

As indicated, if your rate is increased, you may be able to opt out. But there's a catch.

"You may get a notice that allows you to opt out of the change and pay off the card at the current terms. If you do, you must respond quickly to that notice," Detweiler says. "And you must close the account."