Ask Internet entrepreneur and Silicon Valley venture capitalist Reid Hoffman how he decides which companies to invest in, and he’ll tell you he has a simple litmus test to determine whether to give the idea a closer look. “I want to invest in companies that play to one or more of the seven deadly sins,” Hoffman said. For those a bit rusty, those sins would be: lust, gluttony, greed, sloth, wrath, envy and pride. Hoffman, best known as co-founder of LinkedIn, says the business-professional networking-platform most embodies the deadly sin of greed. “In the end, LinkedIn is helping someone earn...