The above considerations on obsolescence would suggest that most of the risk would result from over-concentration of investment in the energy sector. As you note, should energy become cheap and abundant, (come the day!), that would mostly be a problem for energy incumbents and those invested in them. For the rest of society it would be a blessing of great magnitude -- absent serious negative externalities. Unfortunately, those incumbents and their financial allies have strong positions within the existing establishment -- positions which are not usually enhanced by greater transparency to the public. In this situation it is highly rational to anticipate the sort of strategic sabotage Throstein Veblen discussed, IIRCC, in Theory of the Business Enterprise.

"It is not necessary to have hope in order to persevere."