Years ago, Clark did an experiment to see if banks purposely hold credit card payments to trigger late fees and ruin your credit. So for 8 months, he sent in his payments by overnight express mail shortly before they were due. During that entire time, the company posted his payments anywhere from 4-9 days after they had been received. When Clark called customer-no-service for an explanation, the representative blamed the U.S. Postal Service. He escalated his complaint to media relations and got a response of no comment. That alone speaks volumes.

Fair Isaac -- the originator of the FICO score -- knows that the banks are playing dirty pool. So Fair Isaac is looking at revising its credit scoring model by the spring. Previously, a late pay on your credit report would demolish your FICO score. Under the revision, an occasional late pay will not harm your score, but a pattern of late payments will destroy it. Also, applying for instant store credit won't take the bite out of your credit score that it once did. However, being an authorized user on an account will no longer help your credit score and may hurt it going forward.