Kass also tells Barron's he thinks "the salad days for insurance, which is the cornerstone of Berkshire's business, are over."
Kass has been making the case against Berkshire in his writings on TheStreet.com, including a list of 11 Reasons to Short Berkshire, posted on March 10. Calculated from that day's close to today's close, Berkshire Hathaway is down 5.7 percent while the benchmark S&P is up 12.0 percent.
Today in Kass' Q&A Left Me Wanting More on TheStreet.com, Marek Fuchs takes issue with Kass' Berkshire concerns, and the Q&A format of the Barron's interview, which Fuchs says makes it "hard to frame, challenge or dispute the subject's thoughts and claims." (Fuchs praises some of Kass' other short calls.)
Kass isn't the first to argue over the years that Buffett has lost his touch. Many of those who have bet against him in the past have lost out in the long-run. It's very hard to argue with the world's richest man.
Still, in the short-run of the last few months, Berkshire has dropped while the market has gained, giving some support to Barron's own call last December to "Sell Buffett" when Berkshire was going for $143,000 a share.
While even Buffett himself has warned repeatedly that Berkshire won't be able to match its past performance, he can't be happy when it underperforms the market.
The important thing to remember, however, is that Buffett doesn't look at the short term. He's grades Berkshire's performance on a much larger scale of years, not months. Indeed, both could conceivably claim victory if Kass is able to profit from a relatively short-term Berkshire decline while Buffett and the faithful hold out for the long-haul.
Current Berkshire price:
See Warren Buffett Watch on CNBC's The Call, most weekday mornings at 11:50a ET
Questions? Comments? Email me at buffettwatch@cnbc.com