http://en.wikipedia.org/wiki/Michael_Lewis_(author)
SF Giants / Oakland A's Rivalry: The A's have also established a strong geographic rivalry with the San Francisco Giants. It is generally acceptable in Northern California (unlike in other two-franchise baseball markets like New York, Los Angeles, and Chicago) to identify oneself as a fan of both baseball teams. The teams faced each other in the 1989 World Series, which the A's won in a four-game sweep, interrupted by the Loma Prieta earthquake. During that series, caps were sold with both team's insignias on the front, and the respective colors making up half the hat.
The Giants and A's also enjoyed a limited rivalry at the start of the 20th century prior to the emergence of the Yankees when the Giants were in New York and the A's were in Philadelphia. The teams were managed by managing legends John McGraw and Connie Mack, who were friendly rivals and considered to be the premier managers during that era. Each team played in 5 of the first 15 World Series (tying them with the Red Sox and Cubs for most World Series appearances during that time period). The Giants and A's met in 3 World Series, with the Giants winning in 1905, and the A's emerging victorious in 1911 and 1913.
After a decade-plus of interleague play, the A's hold a 43–36 edge against the Giants head-to-head through May 29, 2010[6]. In addition, the A's have played in six World Series (winning four of them) since moving to Oakland in 1968, while the Giants have only been to three World Series (losing all three) since moving to San Francisco in 1958. When factoring in the World Series matchups between the two franchises (dating back to 1905), the A's hold the all-time edge over the Giants in head-to-head play, winning 56 games and losing 43 times—the Giants won the 1905 World Series four games to one, while the A's won the 1911 World Series (4–2), the 1913 World Series (4–1) and the 1989 World Series (4–0).
