In the past twenty-five years of MLB play, there has only been one forfeit. On August 10, 1995, the St. Louis Cardinals were visiting the Los Angeles Dodgers, and leading the game 2-1 as the Dodgers came to bat in the bottom of the 9th inning. The Dodgers had given away thousands of baseballs to fans coming to the game as a promotion. The first batter, Raul Mondesi, was called out on strikes and then ejected by home plate umpire, Jim Quick, for arguing, as was Dodger manager Tommy Lasorda immediately after. The crowd became agitated, and soon Dodger fans began throwing baseballs onto the field of play. The Cardinals left the field and the baseballs were removed, but when the fans started throwing balls again after the Cardinals came back onto the field, the umpires declared a forfeit by the Dodgers.
The 1970s saw two of the most famous forfeits in baseball history. Ten Cent Beer Night, a promotion held by the Cleveland Indians on June 4, 1974, backfired when intoxicated Cleveland fans jumped onto the field and attacked Texas Rangers outfielder Jeff Burroughs. Umpires declared a forfeit win by Texas.
Five years later, on July 12, 1979, the Chicago White Sox held Disco Demolition Night, in which Chicago radio personality, Steve Dahl, came onto the field to blow up a box full of disco records between games of a doubleheader. Rioting fans stormed the field and the game was postponed. American League President Lee MacPhail later declared the second game of the doubleheader a forfeit victory for the visiting Detroit Tigers.
I was looking up how to spell "forfeit" and I learned that all Major League Baseball forfeits have been caused by stupid publicity stunts.