Up until June 2014 you could transfer American Express Membership Rewards points to whomever you wish. At that time they instituted new restrictions without warning: they would only allow transfers of your points to people who have an authorized user card on your account.
That was always the rule but the website never enforced it up until that time. You could link anyone’s frequent flyer account to your Membership Rewards account and transfer points to it. Now there’s a new rule or rather a waiting period to transfer points to someone else’s account.