The title says it all. Let's skip the formalities and dive right in.
1. It encourages you to start with "how," not "why"
As Rob Woodbridge at Unteather.tv points out, going "mobile first" can encourage you to adopt strategies without context. In one important example, TechCrunch advises enterprise-software companies that they should build a mobile app, simply because US smartphone users spend 86 percent of their mobile time in apps, versus 14 percent in mobile browsers.
This is bad advice, because it is handed out generically to all software companies, regardless of who their customers are or what the purpose of their business is. Some tasks just aren't ideal for mobile, no matter how well it's designed. A mobile browser is often a better tool to use than a mobile app for specific tasks, and 57 percent of mobile app time is spent in games and Facebook.
2. "Mobile first" means "simple first," but "simple" actually comes last
"Mobile first" means "simple first," but "simple" actually comes last. pic.twitter.com/nZzUgJjCqz
-- Northcutt (@northcuttHQ) September 23, 2014
One facet of mobile design that's almost impossible to argue with is the idea that it has to be simple, uncluttered, and straightforward. This is, of course, true to an extent of all graphic design, but it's much more true for mobile.
The problem with this is that simplicity is perfection. It's the end result of testing and eliminating features that don't work. It's what happens after you go through a series of revisions and truly define what the core of your business is. You can't start with simplicity. There's a difference between simplicity, or intuitiveness, and reductionism, or minimalism.
A truly simple design is easy to understand but powerful for the user. That is the end result of a long process. You can't start with it unless you're very lucky, or very, very good. It's better to use desktop as a testing ground, where more clutter is permitted, and mobile as a reductionist platform, where only the essentials are in plain view.
3. "Mobile first" prioritizes design trends over value
The phrase "mobile first" encourages you to start with design trends rather than value propositions. Good design starts with value and works from there. In this sense, "mobile first" puts the cart before the horse. It hopes that sleek design will overcome a weak USP.
4. It's usually terrible advice for B2B companies and B2B software
While there are in fact some professions where mobile devices are making headway against desktops, it's unlikely that mobile device use will beat out desktop use for most professions. Our devices may get sleeker, employ touch screens, etc., but for most office work a large screen and a keyboard are necessities. Even the old fashioned mouse is also often preferable to the touch screen, which can fatigue your arm over time. While it's important for these companies to embrace mobile and recognize that some professionals will want to use mobile devices, "mobile first" is certainly a bad strategy today, and is likely to stay that way.
5. It can damage the desktop experience
"Mobile first" design can easily alienate the desktop user, in the same way that non-responsive, non-mobile design can alienate the mobile user.
Jens Boddum recently pointed out how mobile-first design results in a poor user experience for the desktop user at DSB. The desktop version of the site resembles a scaled-up mobile app. Everything is too big, and they still use a hamburger button for navigation. Smaller desktop screens still require scrolling when it's absolutely unnecessary.
This is an example of "mobile first" resulting in misplaced priorities.
Image credit: Susana Fernandez