Jeff Vail argues, counter-intuitively, that suburbanites may be more resilient than urbanites to a economic downturn and energy cost increase:
As long as suburbanites maintain their present income levels, they should be able to afford their present costs of commuting--in most cases rising gas prices won't break the bank, and can largely be addressed through improved efficiency. However, a sharp economic downturn has the potential to dramatically reduce these income levels.
Here’s the key: a sharp economic downturn will most likely reduce urbanites’ income levels by a similar amount. So while these economic troubles may make life in suburbia much more difficult, it will also make life in urban areas much more difficult. Precisely because the issue is base cost of commuting, not variable cost, this economic impact is felt equally in suburban and urban areas. In fact, because there are so many viable (if inconvenient) options for suburbanites to reduce base commuting costs, ...it may be easier for suburbanites to adapt to a sharp economic downturn than urbanites. Cutting down from two commuter cars to one could cut a suburbanite's total expenditures by 10-20%+ per month without great change. That's a large chunk of suburban budgets that is quite elastic, and lends a great deal of resiliency to suburbanite finances. How many urban households can cut expenses by this much merely by doing something as simple as carpooling?