It is preferred to have more than one card if you don't spend them into a deficit.

However if you need to borrow money to start a business, an entrepreneur would do that.

No, not at all....I have a few cards. One I use for all online purchases, one for gas purchases, one for food purchases and one for other purchases. If one card gets compromised (as I’ve had happen with the gas card) the others are not affected. If you had only one card & it was compromised, the credit company could freeze it and you’d have no way of paying via credit. As long as you know how to use the card properly (i.e., don’t charge more than you have in the bank), there should be no problem regardless of the number of cards.

I have 6, i keep my balance low on all of them .. I've been able to greatly enhance my credit score by managing these cards..

Not if you have self-control. I only use a major one for emergencies, pay cash for everything else.

not if you're Super Rich

No 3 lines of credit is a good place to be and keep it at no more than 20 to 30% of the max limit. It's even better if you pay it off monthly and charge every month will build your score faster.

If you want to build up a strong credit history it can hekp th have 2 or 3 as long as they are all paid off before the end of the month

Economists would say no.
Economic theory suggests that if you have one credit card and keep well within it's limit, you should then look around for another that gives 0% interest on balance transfers.
Apply for the second card; transfer the balance from the previous card and pay only what you've spent without interest added, on the second.

But the trouble with theories is that they're impossible to live up to !
So is it foolish to have more than one active credit card ?
YES !

yes, its really tempting to use it.....

Tempting maybe. I don't know about foolish. I've only used one forever. But if I still spent lotta time on the road, I'd get a better deal for buying gas. Same with airfare.

No, it's about safety.