A key reason I think context is still a good and important thing is that it's not just good and important for mobile. Personas are often the closest we tend to get for desktop design, but if you think hard about these, you'll find that some of yours include contextually-useful information. Library computers are different from laptops, which are different from the desktop at the office. Often, these are critically different in technical manners (work computers often do not allow installing plugins), but very often it's as simple as thinking about the degree of focus someone can pay to the task at hand. I've designed a fair number of desktop apps or websites for Customer Care representatives, or Telecom Managers, or others in specific work environments. Long before I thought about mobile context, I put a lot of thought into context of use in this regard. So, why do we spend so much time talking about context for mobile devices? Because they are even more portable than laptops, they can be carried to crazy places. But mostly because they are full of sensors. You can get a lot more information about individual use of a mobile than a desktop if you have access, and try. Trying is a problem. A lot of mobile sites and apps just do their desktop thing, but smaller. Even if you have made a great game or app or site and it's perfectly usable by tapping on a tiny screen, does it work for the context of use. Sure, sometimes I refer to context the traditional way: does it work in glare or darkness. But think about the Desktops (and if you haven't figured that out, laptops are the same) demand attention. If a common use of mobile handsets and tablets is "in front of the TV," then you probably don't want to be totally sucked into the mobile device. You might even need to be able to interact with others, and react at a reasonable speed to the conversation, or the action on the TV. Same for the dinner table, general chit-chat around the house, gardening, or anything else. When I say mobile must be designed with context in mind, I mean that it has to work with people's lives. In that same introduction section where I refer to context explicitly, I also say:
Lives take precedence Mobiles are contextual, here meaning they are used alongside people's actual lives. Desktops (and some and other devices) can suck people in so you can go ahead and issue alerts that blink in the corner of the screen, and they will be noticed. Mobiles are glanced at, used in gaps between conversation and driving and watching TV. They are even used to enhance these other experiences. So make sure they don't interrupt unless they have to. And if they have to, interrupt in a manner they will notice. A blinking LED, for example, is easily missed when a device is glanced at for a fraction of a second.Sure, sure, you might still say I focused too much on distraction and driving. But have you see the task switching studies? Even when just on their mobile, users are interrupted by others, by new updates and by new thoughts of their own all the time (this link has some other great context of use numbers as well). Just because the user is not walking down the street or at dinner, doesn't mean they cannot be distracted. If you are not designing to account for distraction and social context, you are putting up do not enter signs for your users. All that said, context of use is only one facet of design. Check out my other seven Principles of Mobile Design. If you like them, or any of the other content up there you can pre-order the book Designing Mobile Interfaces from Amazon, for a pretty significant discount right now.