Before he created Tumblr—a micro-blogging platform acquired by Yahoo for $1.1 billion—David Karp was a high-school dropout. Bored with his classes at Bronx High School of Science, the bright teenager decided to opt for homeschooling. His mom, Barbara Ackerman, says it was the best decision he ever made. “It became very clear that David needed the space to live his passion. Which was computers,” Ackerman says. Now 26, with neither a high-school diploma or a college degree, Karp is a newly made billionaire. Currently living with his girlfriend in a $1.6 million loft in Brooklyn, the tall, slight brunet still entertains the thought of going to college one day. “At least I should be able to afford it,” he quips.