The third link under the related content section addresses the nano-daimonds that were edited out in the above.

a) Early in the article it states “a little-understood region on the solar system’s edge known as the Oort Cloud” but then goes on to say that based on computer models of this region, we should have 2 to 3 comet impacts in half a billion years. I wouldn’t suggest ‘comets are less likely to smash into Earth’ based on this new study alone;

b) Regarding the ‘and kill us all’ part – In the half a billion years it takes to have 2 or 3 comet impacts from the inner Oort cloud, I’m sure the human race would have successfully achieved mass extinction all on its own;

c) I’m pretty sure that, at our current capacity, we can view a mere 3% of space from earth leaving a 97% guessing game; and

d) Though I find ‘YouRang’ hypothesis of a Halley Comet/Younger Dryas event intriguing, the current scientific evidence points to the introduction (and thus mass imbalance) of cold freshwater into the Atlantic (which in turn, shut down the Gulf Stream) as the likely culprit…. And Halley’s comet is expected to return in 2061.

Please read the last sentence of the article: “Many scientists believe that a collision from an asteroid was responsible for the extinction of dinosaurs from the earth 65 million years ago. ”

The Chicxulub krater (Yucatan, Mexico) is generally believed to be where the asteroid impacted that is the cause of the KT boundary, which is a certain layer between the Cretaceous and Tertairy deposits. The hypothesis, originally proposed by Alvarez in the 1980′s was that this impact would then have thrown up enough dust in the atmosphere to cause somekind of nuclear winter scenario, which would then explain why the dinosaurs died out.

As far as I know, there is no serious disagreement about the impact. The disagreement rises over whether the coincidence (the impact and the extinction happening at roughly the same time – also by the way, the Deccan Traps in India went beserk at this time.. most likely shortly before the asteroid impact) also suggests a causal relation between these events. But while this remains very difficult to prove or disprove, the evidence is stacking up against it.

And that is where I said I get the impression that oftentimes different types of scientists tell a different kind of story. Because of their expertise and/or affinities they look at this very difficult subject from a different angle, so that (overly generalized) astronomers and physicists take one side, the paleontologists the other and geologists are collectively sitting on the fence.

“the Chicxulub – KT boundary – dinosaur extinction connection”
No idea what that means…

So maybe we are even safer than we thought and then again maybe we are under severe threat of something we don’t even have the faintest clue of. In any case as humans we can put comfort in the fact that we are able to and probably will wipe ourselves off this planet far more quickly than nature would.