Should Marinwood-Lucas Valley house 51,000 people to be a "Smart Growth" community?

Lakewood, OH: The Suburb Where Everyone Can Walk to School from STREETFILMS on Vimeo.
Here is a film about Lakewood, OH that Smart Growth advocates brag that everyone can walk to school.  It is roughly the same size as Marinwood-Lucas Valley, but has ten times the number of residents.  I don't know much about the community, but they are calling it a "suburb".  I call a community of 51.000 people a "city".

Do you think it is "smart" to turn Marinwood-Lucas Valley into an urban environment to claim that it is "green"?