Today I was asked whether it is possible to pay back your friends and family with a credit card, in order to earn points.
The answer is yes, through PayPal. But it's not worth it. The person you are paying is dinged about 3% and you earn the equivalent of 1% in points. When paying back friends, stick with cash, cheque, internal bank transfers, or non-credit card PayPal payments.
We rarely think of it, but one of the reasons why credit card companies can give you rewards is because every time a credit card transaction is made the person accepting the payment is charged a few percent of the payment.