Warren Buffett’s stock-picking prowess is envy-inspiring, but his recent comments to Berkshire Hathaway (NYSE: BRK-A) (NYSE: BRK-B) investors suggest to me that Main Street investors ought to press the pause button before buying shares in IBM Corp. (NYSE: IBM), Apple Inc. (NASDAQ: AAPL), and individual airline stocks, such as United Continental (NYSE: UAL).