The vast majority of the developing world. Many countries have never had wired internet but have 3G popping up everywhere. Hundreds of millions of people that have never owned and never will own a "desktop computer" are going to get smartphones by 2015.

Try to remember that the USA is less than 5% of the world's population. Most people don't have a desktop computer and never will. They're starting on smartphones now and as tablets become cheaper they will get those too.