Not all iPads supplement existing laptops. Around 3,000 iPads replace laptops for some employees, such as the field sales force, diagnostics group, and shop floor technicians who don't regularly need a laptop.

As the number of iPads grew, so did mobile apps in Genentech's custom-built enterprise iOS app store. Today, the store has a whopping 110 apps, whereas most private enterprise app stores have only a handful. Every day, Lanzi deploys new apps and retires old ones. Many are time-based or event-driven apps and naturally reach the end of their usefulness.

Most CIOs in the early throes of an iPad rollout don't expect to have much more than a dozen enterprise apps. But Lanzi advises them to prepare for a mushrooming effect. "If you are setting up an enterprise app store today, you've got to expect it to scale to this level or greater," he warns.