Canopy's one-of-a-kind deal is being decried as "value destroying" by an active hedge fund. : Once or twice every generation, a game-changing investment opportunity comes along. Previously, it was the introduction and rise of the internet and internet-based commerce. Today, it's the ongoing legalization of marijuana. How big could the weed industry grow? Although the answer really depends on your preferred Wall Street investment firm, some utopian estimates suggest that the pot industry could one day generate $130 billion to $166 billion in annual revenue.