Investor Doug Kass, on the other hand, says he's rethinking his position. "The problem with this announcement is that the calculation of the company’s intrinsic value is impacted. The upside reward is now reduced... Valuations must now be adjusted."
Buffett's speed in disclosing his condition is a sharp contrast to the decision by Steve Jobs and Apple to delay or withhold release of details of the cancer that eventually took his life.
In a live interview with CNBC in June, 2009, Buffett backed criticism of the company for not immediately disclosing that Jobs had received a liver transplant several months earlier:
"If I have any serious illness, or something coming up of an important nature, an operation or anything like that, I think the thing to do is just tell the American, the Berkshire shareholders about it. I work for 'em. Some people might think I'm important to the company. Certainly Steve Jobs is important to Apple. So it's a material fact. Whether he is facing serious surgery or not is a material fact. Whether I'm facing serious surgery is a material fact."
Buffett tells our Becky Quick tonight that, as has been the case for several years, Berkshire's board knows who would be asked to run the company should Buffett be suddenly unable to do the job.
Buffett reaffirms that the person, as before, does not know that he is the stand-by successor.
Keep up with Warren Buffett on CNBC.com and
follow alexcrippen on Twitter.
Email comments to firstname.lastname@example.org