I believe most people are reasonable. If I see that the people I work with make more or less than me, a decision was made by someone. If that decision is reasonable, the difference is reasonable. I wouldn't be upset, but I would then know what I could do to improve my value, which would make me a better employee.
On the other hand, if employees remain clueless about the compensation of others in their company, they don't know when they could be worth more, and won't be motivated to make it happen. Perhaps companies like this, but they shouldn't, because it removes a very key motivator from your employees. Saving $20k on a few employees isn't worth much if those employees could earn that $20k by providing more of what you want (especially if that nets you significantly more in business value than the difference in their salary).
This is why I don't understand keeping salaries private. Sure, some people are being severely under or over paid, and they'd have to regress closer to the norm or risk upsetting happiness levels of others, but I don't see any serious issues with this.
In my line of work, I generally am required to ask everyone what they make, and some are more hesitant to tell me than others. Some companies are much more transparent about comp than others, but as a rule individual comp is regarded as something not to be shared with others at your company. The hypothetical discussion I allude to in the article could easily be between two people who do not work together, or that used to work together, making the sharing of salary information more of a private matter instead of a company matter.
If employees had the rare ability to fairly critique their performance vs that of others, making salary transparent shouldn't be an issue. Imagine a baseball team that always paid their best player (highest average, value over replacement, some agreed upon statistic) the most money - it would be hard to argue with that. But in companies with multiple employees and no common metric for measurement, it's nearly impossible to expect Employee A to accurately assess his/her own performance related to Employees B, C, and D. Most would have a tendency to think they are a bit more qualified or a bit more productive than they are relative to their peers.
A fictional example. If you squeeze everyone into a narrow band, you'll loose your patio11 star A/B tester. and with him, millions of dollars of easy profit.
If I see he makes $250,000 and I make $150,000, and I ask "why?" and get an answer along the lines of "he provides us with x, y, and z, and those are extremely valuable to the business." Now that's fine, and I am empowered to be treated as a business partner. I can improve myself and provide something more valuable to the company to warrant better compensation with an understanding of what I can look to receive by providing more business value.
But if I have no clue, why would I want to engage with my company on that level? It doesn't even feel appropriate to make such an approach with this nonsensical taboo.
The point isn't to regress people that earn their difference in pay, the point is to regress people who don't earn their difference. An ancillary benefit is to provide everyone with a better understanding of their value and what value they provide the company, which makes it easier for people to grow professionally.