Or not. Cornell has created a self replicating robot, but we hardly have to fear that it will conquer the world. These cute little cubes don't seem terribly threatening, and they don't seem like much.
And, from a practical standpoint, they're not. But, what we have here is a robot, that from a uncontrolled environment, can find resources and employ those resources to construct another robot like itself. And the other robot is smart enough to give it a hand with this job.
Hardly poster children for the "Grey Goo" scenario. For those that have escaped some of the bane of idiocy, the "Grey Goo" scenario basically posits that we'll create nanotechnology with self-reproducing nanites that operate on a molecular level, and they'll start consuming everything and reproducing everywhere.
There's some very good reasons why this is unlikely. The wikipedia thinks so, and this Center For Responsible Nanotechnology points out that we're not dumb enough to create Grey Goo. Even the guy who started all this stuff about Grey Goo doesn't think it's an issue.
In other words, people are faced with a technology they can't understand and react with fear. Sometimes, I look at the world, and wonder how many people I could convince that my digital camera steals their soul, and it seems like a depressingly large number.
At any rate, putting aside my ranting on Grey Goo, what does this self-assembling robot do for us? Well, it puts us on the path of understanding how complex systems can replicate, which opens up a wealth of understanding in fields like biology, geology, and pretty much anything else. Heck, I'm sure that this could find applications in computer security someday, as models based on this replication are used to predict the behavior of virus outbreaks.
But we don't care about that. What about gizmos? How about regenerating materials? We've already created a few, like aircraft parts that automatically seal microfractures in themselves. But what about cars that undent? Last night, I went and enjoyed H2G2 (On Douglas Adams' birthday no less!) and suffered through a trailer for a new Love Bug movie. The saddest part- that technology isn't that far off.