A couple years back when we were negotiating a "blended" mortgage, our personal banker at our bank told me to close all my (zero balance) store credit cards. She said that each card counted against our credit rating even though they were at 0 balance and had not been used in some cases for several years. She explained in layman terms to me that if each card had a limit of $5,000 and I had 4 cards, the bank considered I owed $20,000 because a day after I received a loan from them I could go out and run every one of those 4 cards up to the max.