Actually, competitive markets solved this problem ages ago: Investment in such assets as brand-name capital, the value of which collapses if the firm fails to live up to its promises, sends a clear signal to the market that the firm makes more money by behaving in a trustworthy fashion than the opposite. Advertising is the most obvious example, even given the constraints and mandates enforced by the FDA; that is why virtually all consumers, given a choice between a brand-name drug and its generic equivalent at the same price, would choose the former. Other examples are a long-term commitment to charitable endeavors, indicating that the firm is not a fly-by-night, construction of specialized facilities not easily transferable to other firms, etc.
And so yet again we find a reason that the political attacks on pharmaceutical marketing are mindless, even as we can be amused in supreme fashion by accusations of "misleading advertising" hurled by the permanent Beltway establishment.
[cross-posted from www.medicalprogresstoday.com/blog/]