Zuckerberg, 28, launched Facebook from his college dorm room and grew it into one of the world's most successful businesses. While his wealth has taken a big hit following Facebook's disappointing IPO, he's still worth close to $15 billion, according to public estimates.
2. Sean Parker
The co-founder of Napster (and first president of Facebook) has more than $2 billion to his name. Parker, 32, served as a mentor to Zuckerberg and famously urged him to drop the "the" in the original version of Facebook's name. He was also an early investor in Spotify, the music sharing company.
3. Eduardo Saverin
4. Dustin Moskovitz
5. Scott Duncan
Scott Duncan, now in his late twenties, made billions the old-fashioned way; he inherited it from his late father, who started an energy pipeline company. He is worth an estimated $4 billion and maintains a limited online presence.
6. Fahd Hariri
7. Robert Pera
Pera, a former Apple engineer now in his mid-thirties, founded Ubiquiti Networks, which makes wireless gear. He reportedly still enjoys living frugally, despite the fact that he's worth over $1 billion.
8. Ayman Hariri
Like his brother (#6), Ayman Hariri, who's in his mid-thirties, has an international pedigree: He earned his undergrad degree in the United States, at Georgetown University, and now works in real estate while living in Saudi Arabia.
9. Yang Huiyan
The only woman on the list, Yang Huiyan, who's in her early thirties, gained her billions when her father transferred much of his own wealth to her in 2005. (Her father, a self-made man, started Country Garden, a successful Chinese high-end real estate company.)
10. Albert Von Thurn Und Taxis
This German prince, 28, attended school in Italy and Scotland before returning to his home country. He enjoys race-car driving as well as local energy projects.