Aaron also raised the problem which the larger Free Software community is trying to fix – reduce duplication of work.
Part of why Linux (IMO) succeeded was the duplication.
Because if you carefully evaluate the duplication, lots of it is not really duplication - but it is the choices, we are free to make.
Take away the "duplication" and you end up with something close-minded as Java, Windows or Mac OS.
The only "negative" of the duplication I have seen so far is the hurt ego of the competing developers.
The Linux desktop is more consistent and coherent today than it ever has been as a result, from icon themes to clipboards to compatibility between window managers to IPC to application notifications to application launching to multimedia to ...
The consistency was achieved not because we have single implementation - but because everybody has agreed what should be inside the implementation! Without previous duplication, without seeing the flipside of different design choices, reaching agreement wouldn't have been possible!
I work for commercial ISV. Believe me when I'm saying you from a decade of practical experience that "no duplication" doesn't mean "consistency" or "ease of development". Very very often decisions are rushed for marketing reasons and developers are stuck for years with a "committee design" nobody can change because nobody knows alternatives because we do not allow duplication.