I think the notion of mobile is illusory and will become more so in the future. Devices will increase in sophistication and what used to be ‘not mobile’ is now mobile. I played around with a 11” MacBook Air recently and it felt more mobile to me than my iPad—it’s light, fast, and fully capable. If I had an Air, I would never need an iPad. It gets back to things I’ve written about before where the device is probably secondary to the content. Unless you’re building an app for a specific platform, then you’re building a website, and it should point to greater device independence (see the whole mobile first discussion).