Reuters:  Berkshire Buyback Seen Clashing With Estate Tax Push:

Warren Buffett's $1.2 billion share buyback from a single unnamed investor likely helped that person's estate save substantially on taxes, just one day after the Berkshire Hathaway CEO said the rich should actually be paying more, not less, when they die. With the "fiscal cliff" looming and … taxes set to rise
dramatically in less than three weeks, the timing was seen as
advantageous — and, according to Berkshire watchers, also out of
place in the context of Buffett's recent tax activism. … Berkshire said it bought 9,200 Class A shares from "the
estate of a long-time shareholder," whom it did not name, at
$131,000 per share, a price in line with where Berkshire has
traded in recent weeks. …

Yet given his wealth and his own self-professed low tax
rate, Buffett has been called out in some quarters for not
practicing what he preaches.

Update:  Wall Street Journal:  Berkshire, in Rarity, to Buy Holder's Stock:

The estate that sold the shares did so at a time when many investors
are unloading some of their winning stocks to avoid an increase in the
capital- gains tax next year, and the sale should qualify for this
year's top tax rate of 15% on long-term capital gains. Next year the top
rate will be at least 18.8% for wealthy Americans, because of a new
3.8% tax on net investment income.

In addition, as part of the debate in Washington over taxes and
spending, President Barack Obama has called for a five-percentage-point
increase in the 15% rate, so the top rate could be 23.8%.

Exactly how much a difference the coming tax increase would make is
unclear. One thing is certain: Even though the Berkshire shares were
longtime holdings, the estate appears unlikely to pay tax on all of the
stock's rise over the decades that Mr. Buffett has run the company.
Estates that sell shares pay tax only on increases in the value of
shares after the date of death, according to tax experts.

Mr. Buffett has been a vocal advocate for higher taxes on the
wealthiest Americans, arguing that the most affluent people in the
country should pay a minimum tax of 35% on taxable incomes over $10
million.