Charlie and I avoid businesses whose futures we can't evaluate, no matter how exciting their products may be. In the past, it required no brilliance for people to foresee the fabulous growth that awaited such industries as autos (in 1910), aircraft (in 1930), and television sets (in 1950). But the future then also included competitive dynamics that would decimate almost all of the companies entering those industries. Even the survivors tended to come away bleeding.
Just because Charlie and I can clearly see dramatic growth ahead for an industry does not mean we can judge what its profit margins and returns on capital will be as a host of competitors battle for supremacy. At Berkshire we will stick with businesses whose profit picture for decades to come seems reasonably predictable. Even then, we will make plenty of mistakes.
Avoiding the big mistakes is key. As Charlie Munger has said:
It is remarkable how much long-term advantage people like us have gotten by trying to be consistently not stupid, instead of trying to be very intelligent. - Charlie Munger
Both Munger and Buffett have said this in a variety of different ways over the years. It seems an underestimated factor in their success.