Kenneth Harney reports in today's San Francisco Chronicle on a recent Federal Reserve staff research report that discussed how some credit card issuers may be withholding certain information from the national credit bureaus and, as a result, affecting consumers credit scores.

The Fed researchers did not identify the credit card issuers that intentionally withhold customers' limits. But for 46 percent of the consumers in a random sample of 301,000 credit files to be affected by this score-depressing policy, the creditors involved must be numerous, big or both.

The full study is available for downloading online (PDF).

This Sunday several writers chose to write a cluster of stories about how you should be careful using credit cards.

Humberto Cruz writes about how credit card rewards can have a downside. He talks about how he uses several different rewards cards to optimize his rebates -- the Chase Freedom card for gas because it's offering the biggest rebate on gasoline purchases, his MBNA World Points card at the local supermarket because of its 5% rebate on purchases of groceries between now and the end of the year, etc.

Writing from Rochester, NY, Frank Bilovsky says that the convenience of using credit cards can "bite". He quotes a local book author:

"The ultimate bottom line is if you use a credit card, you are going to buy more than if you don't have a credit card," said Robert Manning, the Rochester Institute of Technology professor and author of the book Credit Card Nation: The Consequences of America's Addiction to Credit. "That ultimately was the selling point to get it into grocery stores."

Finally, Michelle Singletary says to be sure to be careful when paying routine household bills with credit cards.

David Vise reports in the Washington Post on Francis Vitagliano and his 401(k) card. Vitagliano worked with an MIT professor, the late Franco Modigliani to patent the idea over ten years ago.

Vitagliano's and Modigliani's patent (5,206,803 - System for enhanced management of pension-backed credit
) has been licensed by ING and is scheduled to be introduced at a conference tomorrow.

The credit card industry is not opposing the card's introduction, in part because the first 401(k) card will be a Visa card. In addition, ING is willing to sub-license the rights to the product to other financial services firms, which means that eventually there may be 401(k) American Express and MasterCards too.