Okay, bringing this back to where it started so we can wrap it up and get back to Herman Cain's sex life:
When a libertopian says something is "voluntary" they are implying that every circumstance of someone's life is purely the result of that person's decisions. This shouldn't just be obviously wrong to anyone who's lived in the real world for more than a fortnight, but also to libertarians particularly. The point of a market economy is to efficiently allocate scarce resources. If it works well, then growth ticks up a couple percentage points a year and over time there's a bigger pie, but there are always limits and tradeoffs. Not everyone can be rich, despite their best efforts.
"Ah, but the market creates a meritocracy, where the most deserving get their due!" The idea is that the limited resources get divvied up with the bulk going to the most deserving, because of their skill and the choices they made. Again, it doesn't work like that. Not all capital is human capital. Inheriting the company from dad works just as well (notice how many repeat last names on the Forbes 400 richest list). More modestly, it's a lot easier to get a college degree if you don't need to work while taking classes, or worry about debt repayments. Hell, how much is American citizenship and fluency in English worth, in average lifetime earnings?
That's not to say that people don't make their own life decisions or live with the consequences. But different people are given different options and incentives, often from the day they were born, which can have a huge impact on their prosperity and health. It's not out of line for someone to call out the system for not giving everyone a fair shake.
This really ought to be clear during a cyclical recession. There are tens and tens of millions of people who are unemployed, working part-time, or working worse jobs than they had four years ago. Why? Did those people suddenly decide to become poorer? Did their skills and value to the market suddenly evaporate? Or were they victims of a macroeconomic, global phenomenon over which they had no control? It seems not just callous, but obtuse to blame people for being out or work in these circumstances.