“Risk comes from not knowing what you are doing.” Buffett says, “Never invest in a business you cannot understand.” The advice here is obvious but often forgotten, particularly after investors have had some success. The temptation to believe that success in one area you know well allows you to easily analyze another is much greater once you’ve had some good returns, but should be resisted with vigor. Buffett himself has kept out of the technology sector for the most part, given his lack of knowledge of the sector.