Interesting question – and one that doesn’t have a simple answer. Studies show that the average US consumer has three open and active credit cards. Now, whether three cards is ideal is not important. You can have as many credit cards as you wish – what matters is how those credit cards are managed.
If you tend to spend more than you earn, and find yourself just paying the minimum amount due on your credit cards, you are probably better off consolidating all your bills into just one credit card and just have that card. Having limited credit will prevent you from going deeper in debt. If however, you spend within your means, you probably can afford to carry more than 1 or 2.
Some people choose to have a credit card each for Visa, Mastercard and/or American Express simply because they want to be sure that they can purchase anything and not be told that “we don’t accept that kind of card”. However, since most retail establishments now honor both Visa and Mastercard, it is highly unlikely that you will encounter such problems.
So there is no magic number. No one can actually tell you how many credit cards you should or should not have. The only person who can answer this question correctly is yourself.