Doubt is actually tied for that honor with three other films. The record was set (and still stands with company) in 1937 by My Man Godfrey which saw acting nominations for William Powell, Carole Lombard, Mischa Auer, and Alice Brady. 1937 was the first year that the Academy included the category of Best Supporting Actor and Actress, which explains the inclusion of Auer and Brady. Godfrey also holds the "honor" of sweeping the nominations in all four acting categories AND being nominated for Best Director (Gregory La Cava) without a Best Pic nod.
The record for acting nominations was tied in 1949 by I Remember Mama which features the same configuration as Doubt -- Best Actress nomination for Irene Dunne, Best Supporting Actor for Oskar Homolka, and Best Supporting Actress for both Barbara Bel Geddes and Ellen Corby (both of whom would go on to play beloved 70s matriarchs Miss Ellie Ewing and Grandma Walton respectively).
The last time this feat was acheived was in 1966 when Othello garnered acting nominations for Laurence Olivier, Frank Finlay, Joyce Redman, and Maggie Smith without also picking up a Best Pic nod at the same time.
In recent years, They Shoot Horses Don't They?, Only When I Laugh, Victor/Victoria, and Adaptation have all picked up three acting nods without a Best Pic. But four is definitely the record.
And, for the record, none of the nominees listed above brought home a trophy for their work, so Doubt could still earn a place in history come February 22 if Streep, Hoffman, Adams, or Davis takes a trip to the podium.
(For those who are curious, according to my research, the record for most acting nominations WITH a Best Picture nomination appears to be five -- a record shared by Bonnie and Clyde, Tom Jones, Peyton Place, On the Waterfront, From Here to Eternity, and All About Eve.)