In Enemy Quarters

At last year's CeBIT technology exhibition in Hanover, Germany, Juha Christensen spoke about Microsoft as if it were the Evil Empire. As a cofounder of London-based Symbian, he saw himself as a Jedi Knight, intent on European technology winning the day and becoming the Windows of the handset market. Several months later the 36-year-old Swede switched camps. Now, he is helping design the mobile strategy for Symbian's nemesis out of the U.S. as vice president of marketing and services for — you guessed it — Microsoft's mobility group.

Why the switch to the enemy camp? A year ago...