Professor MacDonald is absolutely right about a) in that much of the theoretical underpinning for market economies is that information is freely available to the market. I’d add that, as an assumption, it’s a dodgy one. While auditors, accountants, risk managers and compliance managers are employed, in one way or another to make this assumption true, we’ve seen rather a lot of examples of where it has not been. There’s also the issue regarding the difference between the availability of information and its comprehensibility. If one makes data available but similarly depends on your exchange partner not understanding its import, the same damning ethical judgement obtains, I think.
Point b) is also salient, though I may not have been entirely unambiguous in my original comment. I don’t think that the requirement for equitability is a strict one. In fact, the only requirement is that both parties judge the transaction as equitable. I’m not sure there would be a non-relative way of showing equitability, in any case.
Extending the idea a little further, take for instance the examples of monopolies or cartels. There’s a general view that monopolies and cartels (except in some limited instances) are pragmatically and ethically suspect. The reason for this comes back to the judgement of equitability. If a monopolist charges an above-market rate for his product because there are, by definition, no other sources of that product, his exchange partners may be driven by need to purchase that product with full information. They won’t, however, consider it an equitable trade. In this case, the requirement for full, comprehensible information disclosure is met but there is still a lack of equity and, therefore, ethical good.
As always, my ideas on the subject are open to discussion and further refinement, but I think there is something vital about both conditions for ethical exchange, full information and the mutual judgement of equitability. I’d be interested to hear from anyone who has a different view on the matter.