Apple’s stock, which ran up US$1.40 yesterday alone, could decline after Monday’s Macworld Expo keynote, according to a Wall Street Journal [subscription required] article that suggests any new products will have just a marginal impact on Apple’s market share and bottom line. Morgan Stanley analyst Gillian Munson reveals that in three of five cases after Apple launched a new computer since 1997, its shares slipped. Of those three occasions, the stock fell an average 19 percent in the next six months. Other concerns: Apple has lowered its own growth expectations and world-wide market share still remains at 5 percent. Meanwhile, Apple‘s home page continues to build pre-Expo hype, with today’s Macworld Expo catch phrase “It’s like a backstage pass to the future.”