Earlier quoted context omitted.
Nearly my entire net worth is in BRK.B, and I wouldn't buy at these prices. If you track it's average Price to Book value it's close to the highest ratio it's ever had. I believe it broke over 1.7 last week. When it hit it's all time high P/B ratio of 2.0 in the first internet bubble, buyers returns were very poor for the next decade. I'm hoping for a much bigger sell-off so I can pick up some more below $150.
Seems unnecessarily reckless to put almost all of your net worth into a single stock.
But in this instance, the single stock is a holding company that is already diversified across several industries. Anything that would negatively impact Berkshire Hathaway to a greater extent than the market as a whole is likely to be the product of intentional malice. As it is now, it's akin to an extremely actively managed mutual fund, in that they generally have at least one seat on the board--or at least VIP seats at the shareholder meeting--for anything they invest in.