I recently read Karen McGrane’s Content Strategy for Mobile, which could just as well have been billed a pump-up speech. I highly recommend you get your hands on it, now.

Industry folks have been talking about “the year of mobile” for, well, years. Whether it was really last year, the year before, this year … it doesn’t matter. It’s happening now.

We’ve finally tipped the scales of smartphone ownership, with more than 50 percent of U.S. mobile phone users owning smartphones. But that’s not surprising; we’ve been watching that number creep toward 50 at a predictable pace. More interesting is the increase in mobile content consumption – the ways we are using our smartphones and how much we’re using them.

One in three minutes spent looking at digital content is spent on a mobile device.

And I’m not surprised one bit.

Last night I did something I have never done in my 25 years. I wore an eye mask to go to sleep. Forget your partner’s reading lamp keeping you up – that’s a walk in the park. Try the flashing light of your husband cruising through Flipboard. Mine invariably looks at the news (on Flipboard), or sends emails, or checks our bank account on his phone after I’ve shut my eyes.

Earlier in the evening, we sat on the couch before making dinner. A basketball game was on and his laptop was sitting on the floor, but he was busy researching specs for the new Ferrari LaFerrari (zero to 60 in less than three seconds), on his phone, while I – very “last decade” – lusted over clothing in a print catalog.

The point is (and I’ll quote Karen McGrane here), “If people want to do something on the internet, they want to do it using their mobile device. Period.”

We can’t design or plan for a “mobile use case.” We can’t think we know what people want and don’t want to do on their phones and, most of all, we can’t keep pretending that maybe users won’t notice or won’t care if our sites aren’t optimized for mobile.

Think you can keep skating by? In her book Content Strategy for Mobile, McGrane talks about how whether or not your site is mobile-optimized will soon be an ACLU-style rights issue. Scratching your head? Research shows that if people can’t afford both internet service in their home and a mobile phone, they opt for the phone. More than one-third of Americans don’t have a broadband connection in their home. If your mobile site doesn’t work, or you choose to provide incomplete content to mobile users, you are effectively denying access to a whole sector of the population. Ouch.

In the U.S. and the U.K., 20 percent of internet users are mobile only – meaning they never use a computer to go on the internet – and that number is growing. These users are mostly over 25 and have low income. Thirty-one percent of Americans called themselves mobile mostly.

McGrane applauds the American Cancer Society, or ACS, which provides information to “help you stay well and get well, to find cures and to fight back,” for its mobile content strategy. African-Americans, Hispanics and people with low income are less likely to have access to the type of early-detection cancer screenings and health care that could be lifesavers. They are also more likely to be heavy mobile users.

So, ACS took all its content mobile and made a heck of a site. If it didn’t, it would completely miss its target audience. Anything it did for a desktop site would be a waste – its target audience literally unable to see it. Since ACS launched the new site, mobile traffic has nearly doubled. In this case, whether the content is accessible via mobile could be – not to sound extreme or anything – a matter of life and death.

Think about that.

Now, let’s all get our act together. Mobile content doesn’t need to be exactly the same as desktop content, but it needs to be at parity.

One more quote from McGrane, to finish: “Your user gets to decide how, when and where they want to read your content. It is your challenge and your responsibility to deliver a good experience to them.”