[watwut]

"you're good at X, but the business has changed and Y is driving our bottom line much more than X now, but you have no interest in Y ... he odds of X being that important again in the future are very low"

This should be open discussion whether you have transparent salaries or not. Long before it comes to salary decision, the topic of "we need more Y, learn it" should happen. Not just because of salaries. If transparent salaries force it, then it is a good thing. Not just because of fairness, but because developers often focus on the wrong thing. And because when manager opens it, sometimes it turns out there is obstacle for doing Y that can be overcome with help of manager.

I mean, really. If you valued X in the past and just merely praised people for it and now it is changing to Y, be clear and tell them. It is very unlikely that your ninja coder turns from best to worst overnight just after slight strategy change. If he was so awesome, he will be able to learn new thing fast - unless there is some kind of resentment going on in his head which usually have little to do with strategy.

Non transparent salaries dont prevent people talk, dont prevent resentment either, but you usually end up with humble/shy coders having much lower salaries then overconfident ones. And I seen that humble/shy getting really resentful when he figured it out.