There seems to be an increasing trend of "free" online services to require a credit card while signing up, but then start charging you after an initial period, e.g. LinkedIn Premium is free for the first month, then a monthly fee applies until cancelled.
Is it possible to get a $0 credit card to use if you have no intention of continuing into the paid part of the service? Using LinkedIn as an example, I did sign up for Premium but forgot to cancel it before the next month had started and had to pay for one month, which seems to be what they want to happen and how they make their money (apart from those people who see the value in it and are happy to pay each month).
So, in the initial period, the credit card is good enough to sign up to the free part of the service, but when the company tries to renew it, it is automatically rejected due to insufficient funds.