No, you probably don't want to share your taskbar. You might want to share some other desktop widget, who knows? And that means the configration widget is around for every plasma widget. I don't use it either, but on the other hand, I don't worry about it. I use KDE to get my work done, and my KDE4 desktop allows me to do that in exactly the same way I used my KDE 1, 2 and 3 desktops.
Of course, this has _nothing_ to do with nepomuk and the semantic desktop.
Nepomuk is what you use when you tag brush presets in Krita so you can filter the presets you need in a particular stage of a project or a particular project. Artists like that. So you probably don't need that either, but in this instance, Nepomuk actually _helps_ professional users to get their work done.