Whether you like it or not urbanization is happening. Half of the world's population and 80 percent of Americans live in cities.
And while cities contribute 70 percent of greenhouse-gas emission, global GHG emissions would be much higher if the world's urban population sprawled out into non-urban land. Imagine how many trees would be chopped with all the new single-family homeowners, Hates Idiots.
Just look at the numbers. New York City 7.1 tonnes of CO2 per capita each year vs. the average American's 23.9 tonnes. That's a huge disparity.
I find this study particularly telling:
http://www.smartplanet.com/people/blog/cities/housing-near-transit-uses-less-energy-than-suburban-green-homes/234/?tag=content;col1"The underlying philosophy seems to be that we are to sacrifice all desires for a decent life for the sake of Mother Earth."
People choose to live in cities. You might choose not to live in a city, that's fine. But for the billions who do, it only makes sense to make our cities smarter and more efficient.
At the risk of frightening you even more, gid, it's not just "twenty-somethings" who recognize the importance of dense cities:
http://www.aarp.org/home-garden/housing/info-03-2011/towns-cities-prepare-for-aging-populations.html 
