Yes, Unfriendly organizations are a major threat to humanity. The battle is ongoing. The death toll stands in the tens of millions, much higher if you want to count generously. So yes, unfriendly organizations are a real threat. But they're one that we're all aware of. Luckily, a host of Friendly people and organizations are dedicated to fighting them, studying them, and mitigating their damage. And many people end up counteracting them, simply by living generally good lives.
Taking the long view of history, I believe that, over the last few hundred years, we have been winning this battle. There's news of tragedy every day, but by many measures 2012 was the world's best year ever.
The UFAI threat, if the SIAI argument is correct, is a sudden and irreversible threat that is currently ignored even by those attempting to build AGI. That's why a small group of dedicated individuals has chosen it as their best chance to influence the future. They're applying pressure where they believe it can have the greatest effect. No one has claimed that it was the only threat, just a very important one.
If I understand the Singularitarian argument espoused by many members of this community (eg. Muehlhauser and Salamon), it goes something like this:
I'm in danger of getting into politics. Since I understand that political arguments are not welcome here, I will refer to these potentially unfriendly human intelligences broadly as organizations.
Smart organizations
By "organization" I mean something commonplace, with a twist. It's commonplace because I'm talking about a bunch of people coordinated somehow. The twist is that I want to include the information technology infrastructure used by that bunch of people within the extension of "organization".
Do organizations have intelligence? I think so. Here's some of the reasons why:
I talked with Mr. Muehlhauser about this specifically. I gather that at least at the time he thought human organizations should not be counted as intelligences (or at least as intelligences with the potential to become superintelligences) because they are not as versatile as human beings.
...and then...
I think that Muehlhauser is slightly mistaken on a few subtle but important points. I'm going to assert my position on them without much argument because I think they are fairly sensible, but if any reader disagrees I will try to defend them in the comments.
Mean organizations
* My preferred standard of rationality is communicative rationality, a Habermasian ideal of a rationality aimed at consensus through principled communication. As a consequence, when I believe a position to be rational, I believe that it is possible and desirable to convince other rational agents of it.