News that the San Francisco Museum of Modern Art has raised $250 million in the last six months for an expansion of its building and program is nothing if not jaw-dropping. The first $100 million of the pledge will go toward doubling SFMOMA's endowment. Perhaps a fund-raising motivator: The Doris and Donald Fisher Collection of modern and contemporary art, with 1,100 works by mostly high-profile New York and European artists, will be on a long-term loan lasting 100 years...