I don't think those things are really different. Consider, for the sake of argument, that the doctors are endorsing drugs from the goodness of their hearts for

I don't think those things are really different. Consider, for the sake of argument, that the doctors are endorsing drugs from the goodness of their hearts for the betterment of humanity. What incentive do the pharmas have to pay them? They're not known for altruism. If the payment had no impact whatsoever, they'd save their money. If docs know they might get paid, that's really not ethically different from having a payment agreement in advance.