"Berkshire Hathaway was downgraded to market perform from outperform Monday by insurance analysts at Keefe, Bruyette & Woods who said a recent rally has left the shares fairly valued. Berkshire's class B stock was included in the Standard & Poor's 500 index this year and a lot of mutual funds that track the equity benchmark had to buy, pushing up the price. They also cut their price target on Berkshire's class A shares to $125,000 from $135,000."

I think this is a good sell-side call, and I am not one who typically praises Wall Street analysts. Since it was announced that Berkshire was being added to the S&P 500 on January 26th, the stock has surged nearly 20% in about a month. It now trades for 1.4 times book value and 1.8 times tangible book value. While neither ratio is extremely high, the stock does trade at a premium to both its peers (rightfully so) and near the upper end of its historical average. It appears the S&P 500 announcement has resulted in such a large surge in the share price that I would agree with KBW that buying at current levels is not a very attractive entry point.