The ultimate insider look at the newest titans of tech and what you can learn from their success In 2007, twenty-one-year old David Karp launched Tumblr, a simple micro-blogging platform, on a whim. By 2012, it had become one of the top ten online destinations, drawing 170 million visitors. By 2013, Yahoo had acquired Tumblr for over $1 billion. Just like that, a kid who hadn t even earned his high school diploma was worth over a quarter billion dollars...