Was it google FUD?
Nope, they've qualified their statements about it every time I've heard them talk about it.
Was it just SEO columnists/article writers spreading the idea because they had no other advise on link building to repeat/repackage that week? (a bit like how important social signals were).
Not exactly -- SEO's need work too, and what's easier than to create a bit of FUD by leaving the *may be* and *in mobile search* qualifications Google uses when talking about the impact of having a mobile version of a site, then selling current customers on "how absolutely necessary it is if they don't want their site to be ranked lower...", while leaving off the *on mobile* and forgetting to mention the *may be* pre-qualifier.
Basically, the SEO community edited "may be ranked lower for mobile searches" to something like "You have to have a mobile version or your site's in danger of not ranking."
Anyone think its already happened?
Absolutely -- I think it's an ongoing separation, but a "good pitch" about a mobile version or not having a mobile version impacting your "desktop" rankings doesn't mean it's ever going to happen.
A site doesn't provide lower quality information or a worse experience to a desktop user if there's not a mobile version any more than a site that concentrates only on mobile and somehow "explodes" on a desktop monitor provides a worse experience for mobile users since it's unusable on a desktop.
They're two different platforms, with two different types of user/uses and I would expect there will be more and more separation in the rankings from one to the other, but I don't see how it would make sense to "demote" a site that provides great information [eg WebmasterWorld]
for desktop users, but doesn't have a great mobile experience and can't really cut the info down to a "bite-sized chunk" to give mobile users who are on the go. BTW: Have you ever tried to use WebmasterWorld on mobile? It's next to impossible.