Bull markets are born out of skepticism. Everyone is fearful that there's a giant bubble so all eyes are on the fundamentals. When euphoria sets in, i.e. neighbors and co-workers start telling you how easy it is to make money on stocks, that's when you know you're at the top. We're not at the top and have seen multiple corrections/bear markets over the past 5-6 years.

Berkshire themselves have made investments into Google this year, a company at the center of this supposed "bubble"... make of it what you will but I think the market is setup to do pretty well in the near future.