Your last sentence is very astute, and resonates with me personally. I thought valuations were insane in the late 90s but ultimately gave in. I think that was less than 6 months before the crash!
Regarding exponential growth. We need to think carefully what kind of efficiency improvements can SUSTAIN exponential growth. The adoption of the Internet to the mainstream was a major event. I guess people might be betting that mobile/tablet is another one. I thought this was already priced in about 2 years ago. I can't think of what has changed in fundamentals that justifies the current situation (except for inflation perhaps).
Regarding exponential growth. We need to think carefully what kind of efficiency improvements can SUSTAIN exponential growth. The adoption of the Internet to the mainstream was a major event. I guess people might be betting that mobile/tablet is another one. I thought this was already priced in about 2 years ago. I can't think of what has changed in fundamentals that justifies the current situation (except for inflation perhaps).