A new happiness article came out a few days ago:

http://www.timesonline.co.uk/article/0,,2099-1793873_1,00.html

It even has the mention of "four-wheel-drive:"

Modern humans, stuck with an ancient brain, are like rats on a wheel. We can't stop running, because we're always looking over our shoulders and comparing our achievements with our neighbours'. At 20, we think we'd be happy with a house and a car. But if we get them, we start dreaming of a second home in Italy and a turbo-charged four-wheel-drive.

This is called the "hedonic treadmill" by happiness scholars. It causes us to rapidly and inevitably adapt to good things by taking them for granted. The more possessions and accomplishments we have, the more we need to boost our level of happiness. It makes sense that the brain of a species that has dominated others would evolve to strive to be best.

[...]

At the Royal Institution, Nettle explained how brain chemistry foils our pursuit of happiness in the modern world: "The things that you desire are not the things that you end up liking. The mechanisms of desire are insatiable. There are things that we really like and tire of less quickly -- having good friends, the beauty of the natural world, spirituality. But our economic system plays into the psychology of wanting, and the psychology of liking gets drowned out."