First, I believe the emailer makes somewhat of a hidden assumption when he writes:
...while people naturally might seek to improve their own productivity, some might do so only as a consequence of being "priced out" of their lower productivity...It should be made clear that some people may not be capable of increasing their productivity. I am thinking of people on the left side of the intelligence curve. The farther to the left you go, the less likely they are going to be able to improve their productivity, even if we make the huge leap that more schooling (public school?) will increase productivity in general.
Expanding a bit on the range of the intelligence curve, when one recognizes that entry level jobs may be the best education in terms of increasing productivity, the minimum wage may act to stunt productivity improvement, since entry level jobs are the ones most often impacted by minimum wage laws.
Finally, some guy in a suit showing up on reddit suggests to me how rare of an event this is. If it was a daily occurrence it wouldn't show up on reddit. I suspect that further probing of those standing on corners in suits looking for jobs are either seeking jobs that pay more than market conditions or are seeking jobs where no one thinks the applicants are qualified. Markets clear including job markets. Someone on a corner is looking for a specific kind of job, where no one may want him, rather than a job in general.