[russell]

In the large he's pretty much wrong. In the small, like a startup, of course you have to focus, otherwise you are pretty much dead. However, if you invest in publicly traded mutual funds, the returns from an indexed fund beats nearly all managed funds due in part to the differences in commissions. In agriculture, monoculture is riskier than diversified agriculture, e.g. the Irish potato famine, or the imminent failure of the Cavendish banana. The financial crash was due to everyone following just a few strategies. Even VCs try to diversify their holdings.

His point about understanding each individual investment is good, but if you cant, diversification is a good strategy.