I understand the point you're trying to make with this (social media will definitely abuse the additional knowledge/opportunities they get by having compulsory credit card info), but chargebacks are actually a pretty effective incentive against this. Given that chargeback fees are ~$20-$100 per incidence, you'd only need 5% or less of users calling out the social media site's false charge for that company to be netting a loss.
I would relish the opportunity to cost Facebook $20 because they gave back a couple cents less than they should have.
