In the vein of your comment about Marxism, maybe PIs should be asked these famous questions: "What power have you got? Where did you get it from? In whose interests do you exercise it? To whom are you accountable? And how can we get rid of you?”
It's worse in the sciences, though; a games programmer can go get a different programming job. A slight tweak to the career goals and you go from a realm of gross oversupply to a realm of significant undersupply. What does a highly-specialized organic chemist do?
Per some other comments, the source of the oversupply doesn't much matter to the people in the field.
I don't think this necessarily reflects the "overall defeat of unions in the US", but your philosophical argument does give some food for thought.
For more information, Wikipedia has a summary history of graduate student organization: https://en.wikipedia.org/wiki/Graduate_student_unionization
That being said, the overabundance itself can also be a need for unionization after a fashion: can organized labor influence the number of new students to reverse the trend? Not to mention the general lack of increases in quality of life: wage levels of graduate students have been flat for decades (don't have a graph to point to, but it's in http://www.amazon.com/Economics-Shapes-Science-Paula-Stephan...).
Regardless of where the money comes from most scientists are like small businesses trying to expand or startups seeking investment. If anything the pursuit of short-term wins gets in the way of free thinking or risky projects.
How is a government funded a non-profit anything like "business"? Its a political process, fundamentally. Politics is also competitive. I think the economics analogy is quite flawed (in th GP's comment).
What do you see as the difference here?
"In California, the main universities -- Berkeley and UCLA -- they're essentially Ivy League private universities -- colossal tuition, tens of thousands of dollars, huge endowment. General assumption is they are pretty soon going to be privatized, and the rest of the system will be, which was a very good system -- best public system in the world -- that's probably going to be reduced to technical training or something like that. The privatization, of course, means privatization for the rich [and a] lower level of mostly technical training for the rest. And that is happening across the country." (http://www.chomsky.info/talks/20110406.htm)
"The growth of administrative work has directly resulted from introducing corporate management techniques. Invariably, these are justified as ways of increasing efficiency and introducing competition at every level. What they end up meaning in practice is that everyone winds up spending most of their time trying to sell things: grant proposals; book proposals; assessments of students’ jobs and grant applications; assessments of our colleagues; prospectuses for new interdisciplinary majors; institutes; conference workshops; universities themselves (which have now become brands to be marketed to prospective students or contributors); and so on." (http://thebaffler.com/past/of_flying_cars)
(As for economics vs. politics, we may wonder if it's ideological to separate them.)
Work is work, regardless of whom the work is done for or their income (taxes vs. sales). A worker can be as easily exploited by a state entity as by a corporate one, which is why teachers, firefighters, and police tend to have unions.
Can you elaborate on the 'bizarreness' of my previous comment?
The means of production in academia is overwhelmingly socialized right now. This top-down decision making is both what causes funding to stagnate (since it's up to bureaucratic and political whims) and causes labor issues to fester (since the number of alternate employers is so low).
With that in mind, a call to unionization seems rather futile. There is no body to bargain with, just bureaucrats and budgets. What leverage would a union have against that?
Fixing loopholes in labor laws is overdue, but why unionize and create yet another special interest group? Workers in all sorts of industries, including tech, are exempted from labor laws. Why not start a broader movement to fix those loopholes?