"It's an interesting item to study. It's ruined a lot of people. You can go broke doing it."
"You'll see way more stocks that are dramatically overvalued than dramatically undervalued. It's common for promoters to cause a stock to become valued at 5-10 times its true value, but rare to find a stock trading at 10-20% of its true value. So you might think short selling is easy, but it's not. Often stocks are overvalued because there is a promoter or a crook behind it. They can often bootstrap into value by using the shares of their overvalued stock. For example, it it's worth $10 and is trading at $100, they might be able to build value to $50. Then, Wall Street says, "Hey! Look at all that value creation!" and the game goes on. [As a short seller,] you could run out of money before the promoter runs out of ideas." (2001 Annual Meeting)
"Charlie and I have agreed on around 100 stocks over the years that we thought were shorts or promotions. Had we acted on them, we might have lost all of our money, every though we were right just about every time. A bubble plays on human nature. Nobody knows when it's going to pop, or how high it will go before it pops." (2002 Annual Meeting)
"I had a harrowing experience shorting a stock in 1954. I wouldn't have been wrong over 10 years, but I was very wrong after 10 weeks, which was the relevant period. My net worth was evaporating." by Warren Buffett (2002 Annual Meeting)