Here’s how it will work: Each of Andreessen Horowitz’s six general partners — Marc Andreessen, Ben Horowitz, Jeff Jordan, Peter Levine, Jon O’Farrell and Scott Weiss — will donate at least half of all management fee and carried interest income they earn for the rest of their venture capital careers. It is up to each individual partner to determine where the money goes.

“We’ve been inspired by what John Doerr and Mike Moritz have done by participating in the Buffett/Gates Giving Pledge,” explains Ben Horowitz, whose initial donation was to a program for special needs children and their families. “We hope other venture capital firms are inspired by what we’re doing, and maybe do something similar.”

It’s impossible to know exactly how much money the Andreessen Horowitz partners will ultimately donate through this pledge, but saying “tens of millions” would be a very conservative baseline. The Menlo Park, Calif.-based firm recently raised $1.5 billion for its most recent fund, which likely generates at least $30 million per year in management fees (assuming 2%). The majority of that money goes to pay staff and other firm overhead, but let’s just assume the partners receive 20%. That would work out to $3 million in charitable donations per year, without accounting for fees on past funds.

And then there is the carried interest on investments, which is where successful venture capital firms make most of their money. And, in the case of Andreessen Horowitz, the lion’s share of that carry goes to its six general partners.

The firm is still too young to have had a significant number of distributions, but the pending sale of Instagram means that the firm has nearly paid back investor principal on its $300 million first fund. And, remember, this is a portfolio that includes such companies as Facebook, Foursquare, Airbnb, Lytro, Pinterest and Twitter.

This seems to be the first time that venture capitalists have made such a pledge, although private equity executives Bob Gay and Jon Huntsman Sr. agreed to give away all future carried interest when forming Huntsman Gay Capital Partners back in 2007. Soon after, however, Huntsman scaled back his activities and, earlier this month, Gay accepted a full-time position with his church. Some limited partners wondered if the lack of financial incentive aided in the departures (i.e., some greed is good).

Horowitz shakes off the potential for such troubles at Andreessen Horowitz, saying that half of firm earnings will be more than enough to satisfy its partners’ lifestyles. “We don’t play polo,” he says. “And our skills are better suited for doing this than working full-time at a non-profit… I think this works out better for both us and the nonprofits.”

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