We'll have one hell of a housing boom, and there will be more of everything. At least until we run into infrastructure issues such as providing enough water for everyone. Or perhaps we will have cogged roadways. (Although that probably mean we can start building subways that pay for itself.)

Also, it will let entrepreneurs and startups live on ramen noodles more.

The ironic thing about these "progressive" anti-development policies is that they end up hurting laborers and low income people by suppressing the construction industry. There is a two-for-one solution to high housing prices and falling wages for e.g. Hispanic families.

Water, environment, earthquakes, and NYIB is why the valley doesn't get much more density.

Check out Tokyo (the largest suburban parts) for what the valley could look like with a bit more density; there still wouldn't be that many high rises. Tokyo also has a bit more fresh water to work with.

The roadways are already clogged. Imagine what it would be like if they actually built enough housing.

I would hope that the roadways would be less clogged if people didn't have to commute ten miles.