The city of Berkeley can do what they want.
In talking to Brian, I was mostly griping (as Brian cogently put it) about the fact that traffic saturation in Berkeley has noticeably effected the quality of living/working here, and not in a good way.
I had not intended to really weigh-in on other considerations, like environmental impact, etc. It's been long understood that city dwellers tend to have the least per-capita impact. But as Jack points out, and I definitely agree, if you are going to expand as Berkeley is now doing, it should be through thoughtful planning, and not by finally giving when your arm is twisted.
I moved to Berkeley in 1987. I imagine the transition was already happening, where Berkeley was changing from a wonderful city with a rich history and a unique combination of a cutting-edge university, quirky liberal population and truly international reputation for effecting change, to what it is now, a relatively conservative bedroom community for San Francisco and Silicon Valley with a university that has also become quite conservative. North side and the Berkeley Hills are crammed with SUV's and other gas guzzling behemoths, filled with frenzied parents and their over-achieving children, dropping them off before getting to their white-collar jobs in the city. 1200 sq. foot houses on Sacramento and Cedar are selling for over $1M. Service workers, like police and teachers, can't afford to live here, so they commute in from Pittsburgh. Equally bad, most of these upper-class parents send their kids to private school, as Berkeley schools are no longer safe, let alone provide a quality education.
I'm not at all sure what Berkeley should or could have done to ward off this downward trend. Maybe nothing. The rise of Silicon Valley, and companies like Google paying 20-somethings RSU packages valued at $300K/yr and more, not to mention cash comp. represents a shock to society very hard to predict and even harder to rectify with the arc society had been on prior. But all the same, it is a sad trend. I know I sound like my dad right now when he was my age... :)
Scott