Been looking at the whole RepRap thing with the intention of making one at some point, just not yet as I don't have time, but that is irrelevant to this post...
Now that they can make themselves and there can be a parent-child relationship between machines the idea popped into my head that someone should put together a repository of machines. The idea is simple enough - you register a machine with the repository and get back a unique machine ident assigned by the repository, as well as being able to put in other info such as names (of machine and creating human.), location, date of inception, version, etc. But the fun bit is being able to state the machines parent, or parents if multiple machines were used, by inputting those machines unique codes. (There is the issue that a parent can print a machine or be cannibalised for parts for a new machine, a distinction should be made.) Such a repository wouldn't just show the reproductive history of the machines, it would also show how they spread by location, and be able to give a timeline of the machines conquering the world, or whatever it is that they do.
Right now such a repository would be quite boring, but its now that it needs to be created so that the future one goes right back to the beginning. But I am just throwing this suggestion out there in the hope that someone will go and create it - I could do it myself but my time is tight and it would be better is someone closer to the project did it anyway.
P.S. Location would need to be a multi-entry dated field as machines can move around. Maybe consider the same for owner as that can change. Giving people the ability to indicate if they are willing to print machine parts off at cost price with location data then leads to the ability to match such people up with close people who want the parts. The unique machine code should have two parts - public and private, private existing to prevent people claiming there machine is the child of a machine it is not.