Real-time analytics firm Localytics has issued a report that says 15 percent of all mobile apps are launched while the device they are running on is offline. That's a clear sign that developers would be serving their users better if they built "offline" modes into more apps, according to Ryan Kim of GigaOm. After all, while wireless networks are expanding all the time in the form of 3G, 4G and Wi-Fi, there are still many places where you can't get connected (like in a subway).
Kim is correct is his assertion that developers should keep lack of a connection in mind and build in offline modes to their apps. This is especially true for mapping applications. I travel to foreign countries a lot, and there isn't a better example of when you need access to maps then when traveling internationally. But if you don't want to pay international data fees, you're stuck with using your iPhone or iPad in Wi-Fi zones. This is why I've always been an advocate of aggressive map caching, or even building a feature into the Google Maps app that allows users to download complete tile packs of cities so that they have access to maps when not on a data network.
But Kim makes another excellent argument for offline mode in apps: As a developer you want users to be as engaged with your app as possible. Adding Instapaper-like features (essentially saving content offline) or more aggressive caching to your apps would allow users to use them to some degree even when not connected to a network, rather than getting a useless login screen.
Localytics used its proprietary product to come up with the numbers for offline data use on iOS, Android, BlackBerry and Windows Phone 7 devices by comparing the time difference between when an app was opened and when its analytics data was uploaded to their servers.