But let's be clear, what's good for Mobile is good for your site in general.
I've long held the view that for the most part its bad actors in the web community who are most penalised by Google search updates.
If you link build via spamy techniques rather than creating genuine content, then no amount of money thrown at SEO specialists will help you.
On the other hand, if you work towards building a useful and informative site populated with awesome content, and that site is relatively fast and conforms to good coding practices then you'll weather the storms of most Search algorithm updates.
Why the mobile search update is different
This time it's about specifically targeting a few easily defined coding techniques. Google is doing what it always does with major changes to search and painting with broad strokes. They'll refine the algorithm as more data comes in, but for now they're focusing on sites that are likely to accomodate mobile viewers because the code says that it does.
That doesn't necessarily mean the sites do accomodate mobile viewers - but based on the code they probably do.
In my tests to date those sites based on mobile-friendly frameworks (tested on sites I'd developed withTwitter Bootstrap and Zurb Foundation) passed with flying colours, even if those sites weren't thoroughly optimised for actual eyeballs on actual phones. Sites without code indicating mobile viewports or media queries failed.
What to do about it
Fortunately the resources available for responsive development have become plentiful and well refined recently and we have several frameworks that support responsiveness out of the box. While you can't transplant an existing template directly, it's possible to build up an existing site layout relatively quickly and modify specific styles for a more mobile-friendly view. It's not a one-click solution, but it's faster than a total site rebuild.
Any designer/developer worth their salt these days should be able to confidently support mobile friendly design.
It's not just good practice now, it's a necessity.
