I recommend only carrying around one or two. For me one is a gas rebate credit card and the other is a card that gives the highest rebate on everything else. Then I have a few others that I take out and use every few months so they keep getting reported but I don't carry them in my wallet.
Part of your credit history is how long you've had accounts open so if a card has no annual fee never close it. Just use it once in a while so it keeps getting reported to the bureaus.
The thing about Ben Stein - don't do that because he carries all of his on him! I saw the video clip and he had a pocketbook that was 2 inches thick with credit cards. That wouldn't be recommended.