In the weeks ahead, millions of consumers will use credit cards to charge their holiday gifts, possibly pushing consumer debt to unprecedented heights. The prospect of new debt levels disturbs some economists, who note that delinquent credit card accounts and personal bankruptcies already have reached historic highs. Others contend that personal indebtedness waxes and wanes over time, and that the cycle tends to be self-correcting. Some experts worry that in the years ahead, consumer debt will continue to rise as card issuers use sophisticated marketing techniques to put cards in the hands of students and consumers of limited means. They also predict that the increasing use of credit cards in such non-traditional venues as supermarkets and doctors' offices will further increase the debt load.