Infrastructure is another problem. Public transit, in particular, faces a chicken-and-egg problem: it’s hard to justify transit systems unless there’s sufficient population density, yet it’s hard to persuade people to live in denser neighborhoods unless they come with the advantage of transit access.
This is true, but only because of how we're used to thinking about things. We think little of building highways or major access roads to "nowhere" in anticipation of, or to spur, future development. Inevitably the future development is then automobile-centric, and even when mass transit of sort sounds like a nice idea, it doesn't really fit the existing development patterns.
It doesn't have to be that way, of course. Obviously it makes sense to focus spare mass transit dollars on population centers, but it also makes sense to change the way we think about mass transit and not have those dollars be so sparse. Development corridors could incorporate mass transit from the beginning, at the very least with right of ways preserved and zoning around planned station locations in anticipation of what is to come.