When money gets tight, how does it affect people who are trying to live and spend frugally? I believe that consumers behave in one of two ways when they feel their budget getting pinched: either they start using cash for all of their purchases or, if they’re like my husband and me, they start using their credit cards more.

I know that may seem contradictory for our family to use credit more often, but it works for us. Why? We pay off our credit card bills every month, and we download our credit card statement into Quicken so we can track spending. When we pay in cash, we’re not very good about noting what we spent where. But when we’re toting MasterCard or VISA, we can download our spending habits in one fell swoop, and we like that.

I’ve been hearing tons of stories about how certain charge-card companies are reducing customer’s credit lines or cutting them off all together–simply because the bank doesn’t like where these customers are shopping.

Yes, you read that right. This has nothing to do with customers not paying their bills on time. But it has everything to do with customers shopping in stores where other people who have been delinquent about paying their credit card bills also happen to shop. Basically, this is shopper profiling.

So if you’re trying to stretch your dollar further and have begun shopping in discount stores you might not otherwise have visited before–like a dollar store or even Wal-Mart–you might think twice about using plastic to pay for your purchase.

According to this “Good Morning America” segment on financial profiling, some credit card companies are cutting off customers based on where they shop or, even worse, based on the zip code where they live.

FYI, the guy profiled in the GMA story above set up a new website called NewCreditRules.com to help other, unaware consumers stay abreast of the latest news on credit card companies changing the rules of the game.

The only way I’ve been affected so far is a letter I got last week from the bank that issued my MasterCard, letting me know that they were raising the rate on my Mastercard “due to the current economic climate.” I pay my bills in full each month, so their raising my rate from prime + 11.99% to prime + 15.99% and it won’t affect me that much.

But here was the kicker: the letter said that if I wanted to protest this rate increase, I had 21 days to write to the bank and let them know. Would I then have the opportunity to actually fight for my right to keep the lower interest rate? Nope. Should I protest the new rate, they would close my account immediately. That doesn’t sound very fair at all, does it?

Have you found the rules changing with your credit card companies?