At the risk of getting flak, I always found it such a waste to have both KDE and GNOME desktop and overlapping related apps projects. Both are of course rather succesful, but imagine what the current status would be if people had stayed with one project instead.
Well, the reason there's both KDE and GNOME needs a little historical context. KDE relied (and still does) heavily on the then-closed Qt toolkit. The authors of GNOME wanted to build something basically like KDE, except with entirely free software components. Naturally, they also needed to write replacements for KDE applications too, because they also relied on Qt.
Of course years later Trolltech relicensed Qt under the LGPL so there was no longer any fear of Qt vanishing and KDE having to scramble to find a replacement. But by then, KDE and GNOME had taken different paths, KDE focusing on extreme configurability, GNOME focusing on user-friendliness. And then there were all those people who didn't like either desktop and decided to roll their own to fit their own needs better, and that's fine too.