If I were on the west coast, I would give no shits about east coast valuations. They lost that privilege when they marked mortgages wrong. Keep building rad tech, we'll keep buying it. Sales are all that matters.
Stated less cleverly: The East coast places a premium on assets. There is an expectation that these assets will increase in value. Think mortgages.
The Midwest places a premium on sales. Think GM/Ford and the Detroit auto industry.
The West places a premium on ideas, a la Silicon Valley.
The point being made is that East coast and Midwest investors have very different notions of valuations from West coast investors. Perhaps the recent write downs are unprecedented not because we are in a bubble, but because we've never had non West coast investors be this active on the West coast.
Edit: I'm not terribly opinionated here, just elaborating on the original point.
Culturally, different groups will perceive a company in different ways. The same group will perceive similar companies differently. It's all over the map. In public markets things stabilize to a common view. That's the effect of liquidity. But private markets without that liquidity can have divergent investor perception.
He covers the nitty gritty details on mortgage collapse in an approachable and enlightening fashion. His book lends weight to your assertion about coastal discord.