Apparently, in the few years its been since I worked there, they've stopped hiring full-time employees entirely: now, all hires are part-time. Thus: second-rate health insurance (not that health insurance ought to come from employers in the first place), no retirement plan (not even the crappy Wal-mart stock they pawned off on full-time employees like me), and easier to fire people on a whim. But this has the hidden cost of needing to re-train people from scratch as the n00bs enter the revolving door, and it also sabotages the quality of labor by destroying any sense of loyalty to the company or enjoyment of the work environment. They then respond to falling labor quality by trying to wring even more out of the employees they have, creating a downward vicious spiral as the best employees walk out the door for greener pastures.

I'm cautious of debating this on my much-less-than-perfect knowledge. You may well be right overall. But I wonder if you've given adequate consideration to the possibility that these kinds of practices may simply be nontraditional, but profitable, solutions to certain equations. Sure, there are hidden costs, but with a company like Wal-Mart, with its track record of ruthlessly squeezing money out of anything they possibly can, my first thought is that they simply calculated that the hidden costs don't outweigh the gains you enumerate.