OK I didn't have time to read all the other replies yet, but i am guessing maybe it is a few things.
TV and popular culture may be one thing. We are long past the days of "Good Times" and "Sanford and son" and "All in the Family".
It seems like our media pushes material lifestyles on us-that everyone has to have expensive cars, etc. Who cares about the environment or if we will run out of oil? Everyone on TV has a lifestyle richer that most people I know. And look at music videos.
Look at how material things are marketed at kids before they can even talk!
Most kids have a TV in thier room now.
The parents grew up as baby boomers who want their kids to have everything-the economy has changed. When I was a kid, we had one TV in the house, nobody cared about what brand of clothes anyone wore, there were no video games or Nikes or whatever. Kids did not get killed for the clothes they wore.
Sometimes adults even instill these values on thier kids and make them brand-name concious at 4 yrs old! (I am not saying that you do!).
Life just pushes all this crap on us that makes people feel like a loser if we don't have this, this, and that.
At the bottom line I think that in our culture there the gap between the haves and have-nots is becoming wider and that is making more tension. Where i grew up, everyone was borderline poor and we didn't think that much about who had what-because we were all about the same, anyway.