AGE 24: Evan Spiegel

CEO of Snapchat

What makes him powerful: Right at the fingertips of almost every young person with a smartphone, Spiegel's fleeting photo messaging app has garnered at least 100 million users around the world, making 24-year-old Spiegel a dominant force in tech and in general.

Currently valued at around $10 billion (with Spiegel himself at $1.5 billion), Snapchat keeps evolving to keep up with users' changing wants and needs. In addition to offering disappearing photos and videos, it has added a new feature called Discover, which plays video clips from ESPN, CNN, and other content partners. The red-hot app also threatens other social media platforms: Facebook tried to buy it for more than $3 billion, but it's looking like a smart choice that Spiegel said no.