American Express (NYSE: AXP) saw a big sell-off in its shares during the after-hours session on Monday following the release of its second-quarter earnings numbers. The shares already closed down over 11%.

It isn't difficult to comprehend this one. According to Earnings.com, Wall Street was hoping for the credit company to make 83 cents per share. American Express only delivered 57 cents per share from continuing operations. Not only did the company disappoint the Street by a very wide margin, but it disappointed itself, since that 57 cents per share represents a 35% drop compared to the bottom-line results achieved a year ago.

Yep, the financial crisis is still with us. American Express needed to significantly add to its credit reserves. Management stated that the economy is having a negative effect on its cardmembers, and that previous guidance can no longer be relied on. Translation: don't buy this stock! At least, that's my opinion.

I simply can't see allocating investment funds to American Express at this point. If investors wanted to get some exposure to plastic, all they would need to do is consider Visa (NYSE: V) or MasterCard (NYSE: MA). Both of these businesses are based primarily on transactions, not on credit risk. Whenever a card is used, these businesses get a little cut. And that adds up, my friends. Granted, both of these companies sold off on Monday and have been weak lately, and they have litigation risk, but I'd at least look at them for the long-term. Over time they should do well.

American Express, however, is way off my list of potential investment ideas. Not even going near this one. Name a timeframe (e.g. year-to-date, one-year, five-year, etc.), and you'll find that the stock is down. The economy is going to have to turn sharply before I even remotely consider it.

Disclosure: I don't own any company mentioned; positions can change at any time.