alt Hacker NewsA prosperous middle class is not a requirement for capitalism to work, and there are more capitalist systems where that's not the case than where there is.
The upper class live in walled neighborhoods with private guards. There's a small merchant class, and then the majority of the population are working class. Much of Central and South America live like this.
There was no middle class to speak of while living under communism here in Eastern Europe. We were all queueing for food equally. Except the nomenklatura, of course.