Most readers will have heard of Mr Buffett. Mr Portnoy is a 43-year-old, mainly famous for setting up the popular American blog, Barstool Sports
Buffett's comments come a day after JPMorgan & Chase Chief Executive Jamie Dimon said he regrets calling bitcoin a fraud
The results were released one day before Berkshire's annual meeting in Omaha
Berkshire Hathaway substantially increased its holdings of Apple stock in the December quarter