The number of credit cards a person has is not as important as what is done with those credit cards. Having too many cards can negatively affect a credit score and the ability to obtain loans. You should have between three to five credit cards at most.
Additionally, care should be taken to keep the balances on the credit cards no higher than 20 to 30 percent of the credit line available. Any more than that and credit scores are affected negatively. It is better to have a credit card or two with low balances and no delinquency history than to have multiple credit cards with delinquencies or high balances.