Since the HTML design principles (which are effectively design principles for modern Web technology) were published, I've thought that the priority of constituencies was among the most important. It's certainly among the most frequently cited in debates over Web technology. But I've also thought that it was wrong in a subtle way.

I'd rather it had been phrased in terms of utility, so that instead of stating as a rule that value (benefit minus cost) to users is more important than value to authors, it recognized that there are generally more users than authors, which means that a smaller value per user multiplied by the number of users is generally more important than a somewhat larger value per author, because it provides more total value when the value is multiplied by the number of people it applies to. However, this doesn't hold for a very large difference in value, that is, one where multiplying the cost and benefit by the numbers of people they apply to yields results where the magnitude of the cost and benefit control which side is larger, rather than the numbers of people. The same holds for implementors and specification authors; there are generally fewer in each group. Likewise, the principle should recognize that something that benefits a very small portion of users doesn't outweigh the interests of authors as much, because the number of users it benefits is no longer so much greater than the number of authors who have to work to make it happen.

Also, the current wording of the principle doesn't consider the scarcity of the smaller groups (particularly implementors and specification authors), and thus the opportunity costs of choosing one behavior over another. In other words, there might be a behavior that we could implement that would be slightly better for authors, but would take more time for implementors to implement. But there aren't all that many implementors, and they can only work on so many things. (Their number isn't completely fixed, but it can't be changed quickly.) So given the scarcity of implementors, we shouldn't consider only whether the net benefit to users is greater than the net cost to implementors; we should also consider whether there are other things those implementors could work on in that time that would provide greater net benefit to users. The same holds for scarcity of specification authors. A good description of the principle in terms of utility would also correct this problem.