I wish expiring credit card numbers existed to kill this sort of online quasi-scam (let's call it what it is).

I'd like to say, "$0.99 a week for 4 weeks? Cool, here's a temporary number that expires in exactly one month. Please cut my subscription off after then."

Of course, I suspect that the benefit of the entrenched system in the US for everyone but consumers will guarantee that this will be really difficult to accomplish in reality.