I would submit that greed exists as part of the human condition, regardless of capitalism, statism, Marxism or any other -isms.

Whether you lean towards Austrian economics or Socialism... greed simply exists and some people will act on it, regardless of the infrastructure they find themselves in.

Capitalism is simply a framework; a vehicle.

There are always going to be a few idiots — maybe we should label them "mentally ill?" — who believe they should own and control ALL the "marbles," because that's what makes them feel "powerful." Maybe they didn't get enough candy when they were kids...

Most theories are pretty amazing... until you actually get people involved in them!