As computers/robots get better and more versatile, they inevitably "compete" for jobs and provide downward wage pressure the same as if the skilled human labor pool (but not the human consumer pool) had drastically increased. Fundamentally it's all about who can do the job better and/or cheaper. If you aren't the one at the top of the "better" or "cheaper" list in some category, you don't have a job. Period.

As a simple thought experiment, imagine a world in which a computer or robot could do literally any job a human could do better and cheaper than a human could do it. In such a world, the only reason a human would draw a salary would be due to charity, not good business sense. Of course, in such a world you don't have an economy as we know it either, which is kind of the point. Our current social contract won't survive in that kind of a world. We'll need a new one.

You might argue that such a day will never come; that there will always be a large class of jobs that humans can do better or cheaper than machines. Perhaps that's true. But that's what this conversation is really about: do machines have fundamental limitations due to physics that will keep them below the level of a large majority of humans forever? I think that's a strange position for most of us at HN to be arguing. Even software development will someday be automated to a large extent, I expect (yes, not anytime soon), and then where will we be?