The threat from those who oppose this line of thought is that, without "incentives", people will stop working. The worst-case scenario is that tens of thousands of people who hold jobs in finance, corporate management, and the professions (not to mention professional sports and acting) will quit their jobs and end their careers because they did not truly want to be bankers, lawyers, CEOs, actors, ballplayers, et cetera. They were only doing it for the money! Actually they wanted to be high-school teachers, social workers, general practitioners, stay-at-home parents, or criminals and layabouts.
Far from this being a tragedy, this would be the greatest single triumph of human emancipation in a century. A small portion of the rich and unhappy would be freed at last from the slavery of jobs that aren't their life's work--and all of us would be freed from an insane system.
If there is anyone working a job who would stop doing that job should his income--and all his richest campatriots' incomes--drop to $100,000 a year, he should not be doing that job. He should never have been doing that job--for his own life's sake. It's just not a life, to do work you don't want to do when you have other choices, and can think of something better (and have a $10,000 cushion to supplement a different choice of life). If no one would choose to do this job for a mere $100,000 a year, if all would pursue something else more humanely valuable; if, say, there would no longer be anyone willing to be a trader, a captain of industry, an actor, or an athlete for that kind of money--then the job should not exist.
there's obviously more to examine here--what should the actual ceiling be, what effect would that have on inflation etc, how do you ensure quality of life for everyone is preserved--but it's a good line of thought that i pretty much agree with