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From the New York Times:

Civil Liberties Group Loses $20 Million Donor

A longtime anonymous donor to the American Civil Liberties Union has withdrawn his annual gift of more than $20 million, punching a 25 percent hole in its annual operating budget and forcing cutbacks in operations.

Anthony D. Romero, executive director of the A.C.L.U., acknowledged in a written statement that a ”family” had told the organization in September that it could not make its annual gifts, at least for next year. ”This family, that has sought to protect its privacy by arranging its gifts anonymously, notified us last month that due to market conditions it will be unable to make its expected sizable donations of over $20 million,” Mr. Romero said.

A.C.L.U. board members, who insisted on anonymity because the loss of the gift was reported in an executive session of their meeting, identified the donor as David Gelbaum, who made a fortune as a hedge fund manager and is now better known as a major investor in clean technology. ...

Mr. Gelbaum began contributing $50,000 or so annually to the A.C.L.U. in the early 1980s and kept increasing his gifts, to $22.5 million in 2008, board members said.

The only condition he placed on the gifts was that he remain anonymous, so only a handful of people at the A.C.L.U. knew he was the donor. ... Mr. Romero did not reveal Mr. Gelbaum’s name, describing him only as ”a donor,” board members said

Still, it is hard to keep secrets with a board of more than 80 members, most of whom report to state affiliates. ”As soon as he started telling us, anyone who had a laptop with them was busy Googling” and figured out who the donor was, a national board member said.

Mr. Romero told the board that the donor had also stopped giving to three ”sister organizations,” a phrase board members said he had used in the past to describe other groups with which the A.C.L.U. has collaborated, like the Sierra Club.

Mr. Gelbaum took a rare turn in the spotlight earlier this decade when environmental activists said he was behind the Sierra Club’s decision to adopt a neutral stance on immigration. Some people believe immigration has aggravated environmental problems.

He had given the organization a total of $101.5 million, according to The Los Angeles Times, which wrote what is perhaps the only major profile of him, in 2004. In the article, he is quoted as saying that he told Carl Pope, the Sierra Club’s executive director, in 1994 or 1995 ”that if they ever came out anti-immigration, they would never get a dollar from me.”