Cleantech entrepreneurs aimed for more than just success as most businesses define it. The cleantech bubble was the biggest phenomenon—and the biggest flop—in the history of “social entrepreneurship.” This philanthropic approach to business starts with the idea that corporations and nonprofits have until now been polar opposites: corporations have great power, but they’re shackled to the profit motive; nonprofits pursue the public interest, but they’re weak players in the wider economy. Social entrepreneurs aim to combine the best of both worlds and “do well by doing good.” Usually they end up doing neither. The ambiguity between social and financial goals doesn’t help. But the ambiguity in the word “social” is even more of a problem: if something is “socially good,” is it good for society, or merely seen as good by society? Whatever is good enough to receive applause from all audiences can only be conventional, like the general idea of green energy. Progress isn’t held back by some difference between corporate greed and nonprofit goodness; instead, we’re held back by the sameness of both. Just as corporations tend to copy each other, nonprofits all tend to push the same priorities. Cleantech shows the result: hundreds of undifferentiated products all in the name of one overbroad goal. Doing something dif erent is what’s truly good for society—and it’s also what allows a business to profit by monopolizing a new market. The best projects are likely to be overlooked, not trumpeted by a crowd; the best problems to work on are often the ones nobody else even tries to solve.