Many Starbucks (NASDAQ:SBUX) and Wendy's (NYSE:WEN) locations have been accepting credit cards for payment for a while now, and competitors such as Burger King will soon accept them at most locations, too. On Sundays, most churches across America have long collected offerings in the form of cash and checks. But now some churches are accepting charge cards, as well. Heck, you can even pay your income tax and gas bills with plastic.

While more and more merchants are accepting plastic, more and more Americans are using cards for more and more purchases. A recent Wall Street Journal article noted, "For the first time, Americans used cards -- credit, debit and others -- to buy retail goods and services more often than they used cash or check in 2003."

The article also cited some telling statistics:

  • The percentage of American households with payment cards: 73%, vs. just 16% in 1970.
  • Average cards held per household: 0.6 in 1971 and a whopping 7.8 in 2003.
  • Number of merchants that accept cards: 820,000 in 1971 and 5.3 million today.
  • The number of card solicitations that will arrive in our collective mailboxes this year: nearly 5 billion. (Yes, billion!) There are only some 300 million Americans, at most, and roughly 106 million households -- so that's 17 offers per person and 47 per household. Jeepers.

Is this trend a good thing? Well, it sure seems so for card concerns such as MBNA (NYSE:KRB), American Express (NYSE:AXP), Capital One Financial (NYSE:COF), and Citigroup (NYSE:C). It also offers consumers some benefits, such as convenience. But there's a catch: When we pay with plastic, we tend to spend more, perhaps because the cost doesn't seem as real.

Another way to think about it is this: If you're charging all kinds of little (and big) discretionary purchases on plastic and you're accumulating credit card debt, you may be paying interest on that cheeseburger value meal for more than a decade! It can end up costing you several times what you paid for it -- hardly a value now, eh?

Be vigilant with credit. It can be a wonderful tool and convenience, but its dark side is dark indeed -- and dangerous. Learn a lot of important things about how credit works in our Credit Center -- where you can also order copies of your credit reports to make sure they're not among the majority with errors in them.

Longtime Fool contributor Selena Maranjian does not own shares of any companies mentioned in this article.