First, a digression. I, like Glaeser, think The Lorax is a very good lesson on externalities and public goods and the importance of protecting the environment in the face of market incentives that will not. However, the Once-ler is not an archetypical capitalist as I assume Seuss intended, in fact he is a miserable failure of a capitalist. He fails to replant trees to ensure the future success of the business even though the incentives to do so are clear. However, in his willingness to go after the short-term gain and sacrifice the long-term health of the business, he is perhaps a good model for the bank executives that managed to screw that industry up royally.
Anyway, I believe in density and I believe the future of humanity is largely urban, not rural. I understand urban living has drawbacks: lots of concrete, heat islands, etc. But on balance (and in general) the ability to live efficeintly is greatly enhanced in urban areas and Glaesers research seems to confirm this. So I look very favorably on residential high rise developments in the city center because it is important to have downtown residents that live and work locally.
Personally, I chose to live in my neighborhood in Portland because from my house I can walk a few blocks to the park, the library, a New Seasons and a QFC (this was especially handy during the big snow storm), the bakery, coffee shops, restaurants, the bank, the hardware store and even the river. I am close to a multi-use path that takes my wife and her bike downtown to work most days, I can walk with my children to their schools and there are bus lines a couple of blocks away. I rarely have to get in my car to do anything. When I lived in Corvallis, I was in and out of my car all the time, because though it is a nice bucolic college town it is spread out. I feel my current lifestyle is healthier for me and my environment.
This is not to say that I pass judgement on those that choose to live in rural areas, but as a general trend I hope to see more density in America's urban cores and less sprawl to the exurbs. If you want to see what that is like, visit Denver - though the downtown has come a long way in the last 10 years it is still largely deserted after business hours.
But this vision of an urban ideal does create some conundrums. My wife and I disagree, for example, on agriculture. I tend to think some aspects of large scale agriculture is good. Production happens where it is most viable, economies of scale are large and a relatively small number can support all of the urban residents. My wife is very supportive of local agriculture, the farm-to-table movement and has, as an ideal, small local farms that sell directly to urbanites and do not rely on chemical fertilizers and pesticides. There are valuable aspects to both systems and it is hard to know where the right balance is, but I worry that this local ideal is highly correlated with wealth and it does not provide answers for the poor depend on highly productive agricultural sectors.
Clearly the two sectors, urban and rural, are complementary and we would not be able to live densely without the support of rural agricultural areas. But finding the balance between living efficiency and sustainably on one hand, and being less reliant on industrial agriculture and living 'closer to the earth' is not an easy task - nor is the appropriate balance obvious.