Is Barron's right? Nobody knows what the future value of Berkshire's businesses are -- although I am sure Warren Buffett's estimates of that value are more accurate than Barron's. And Buffett opted not to comment in the article.

But I think Barron's is right to question the long-term value of Berkshire stock. That's because its competitive advantage is capital allocation. And the master capital allocator is Warren Buffett. He is searching for a replacement from outside the company which suggests that Buffett has failed to develop a successor. This is important because as Berkshire is currently configured, it will continue to generate at least $10 billion a year in cash that needs to be invested.

I spoke with a New York money manager who has enjoyed the doubling of Berkshire's stock over the last several years. He told me on Thursday that he thought Berkshire had run up to the point where it was at least fully valued. I would not be surprised if more money flows into Berkshire stock over the next few years due to the volatile markets and the desire for a safe haven.

But when Buffett inevitably leaves the CEO position, investors will sell the stock. There is simply no way to know whether Buffett's designated successors will be able to create shareholder value as well or better than he has. If after a few years, it's clear that those successors are up to the job, then the stock will rise. If not, then selling now will look like a pretty good decision.

That's the risk of investing in a company that depends on one outstanding person to make its most important decisions.

Peter Cohan is president of Peter S. Cohan & Associates. He also teaches management at Babson College and edits The Cohan Letter. He has no financial interest in Berkshire Hathaway.