The Giving Pledge, invented by Bill and Melinda Gates and Warren Buffett to spur the philanthropy of billionaires, is one year old. In Fortune’s July 5, 2010, cover story about this startup enterprise, we called it “the biggest fundraising drive in history,” and so far it’s delivering. To date, 69 billionaires (often signing with their spouses) have made the pledge: a commitment to give at least 50% of their wealth to charity during their life or at death.

Old money — of the David Rockefeller kind — is visible on the pledge list. But self-made wealth is the rule, and assuredly the coolest recruits are Facebook co-founders Mark Zuckerberg and Dustin Moskovitz, who each turned 27 in May. Moskovitz is shown above with the young woman he lives with, Cari Tuna, 25, whom he describes in his letter posted on Givingpledge.org as his “partner” in philanthropy. She was busy graduating from Yale while he was dropping out of Harvard.

Moskovitz left Facebook in late 2008 to start Asana, a San Francisco software company aimed at improving productivity within small groups of business workers. But he is still a 6% owner of Facebook, which raised capital this year on terms that valued the entire company at $50 billion. That valuation gives Moskovitz a paper wealth of $3 billion. Zuckerberg’s 24% of Facebook places his fortune at $12 billion.

Zuckerberg’s out-of-the-blue announcement last fall that he would give $100 million to Newark’s schools made huge news. Since then he’s been quiet on the philanthropy front.

Moskovitz’s giving has so far been totally out of sight. But that could change: His girlfriend, Tuna, has quit her job as a Wall Street Journal reporter and has begun, he told Fortune, to work full-time on “the philanthropy side of our world.”

Both intellectual and idealistic, Moskovitz says he is drawn to metaphilanthropy, an obscure word he defines as “work relating to philanthropy.” Givewell.org, which evaluates charities (and which, for example, praises Doctors Without Borders), is a metaphilanthropy enterprise to which Moskovitz has contributed.

In time, he says, philanthropy will get almost all of his money. He himself grew up in comfortable, though not wealthy, circumstances in Ocala, Fla., where his father practices psychiatry. Envisioning children of his own, the son says, “I think it’s not that healthy for kids to inherit a lot of money.” The ceiling in his mind right now: perhaps $10 million for each child.


Read more about some of the lesser-known billionaire givers
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The signers:

(Wives who co-signed with their husbands, but who are not pictured, are listed in parenthesis under their husband’s picture.)

John (and Karen) Huntsman, Laura and John Arnold, Lee (and Toby) Cooperman, Annette and Harold Simmons, Charles (and Merryl Snow) Zegar