To its fiercest devotees, one of the best things about the BlackBerry is its carefully designed physical keyboard, which the skilled BlackBerry addict can play like a violin. These folks scorn Apple's popular iPhone, whose keyboard is virtual and must be operated by tapping on the screen.

But, on Friday, Verizon Wireless and Research in Motion, the BlackBerry's maker, will do the unthinkable: They will introduce a BlackBerry model without a physical keyboard, one where typing and navigating require tapping on glass, just as...