One way or another, there's really no way for the economy to grow strongly and consistently unless middle-class consumers spend more, and they can't spend more unless they make more. This was masked for a few years by the dotcom bubble, followed by the housing bubble, all propped on top of a continuing increase in consumer debt. None of those things are sustainable, though. The only sustainable source of consistent growth is rising median wages. The rich just don't spend enough all by themselves.
The flip side of this, of course, is that rich people are going to have to accept the fact that they don't get all the money anymore. Their incomes will still grow, but no faster than anyone else's.
How do we make this happen, though? I'm not sure. Stronger unions are a part of it. Maybe a higher minimum wage. Stronger immigration controls. More progressive taxation. National healthcare. Education reforms. Maybe it's just a gigantic cultural adjustment. Add your own favorite policy prescription here.
This isn't just a matter of social justice. It's a matter of facing reality. If we want a strong economy, we can only get it over the long term if we figure out a way for the benefits of economic growth to flow to everyone, not just the rich. This is, by far, Barack Obama's biggest economic challenge. Until median wages start rising steadily and consistently, we haven't gotten ourselves back on track.