The premise behind the RepRap project is to build a machine that can reproduce itself. While it's not quite able to accomplish that task entirely, it can produce a great many of its own parts.
That's exactly what's going on at the University of Washington, where they seem to have set up a "RepRap Breeding Center". So far a team of two students have produced three working RepRap Mendel units within one class term. From Open3DP:
In a post quarter meeting, we predict that we could fabricate about one Mendel a week with a slightly larger team of players. We coined the concept of our lab becoming a “Rep Rap Breeding Center”.
It seems that RepRaps and in particular the Mendel version, have gone viral. What might the population of RepRaps be today?