I think we should just merge [tag:gnome3] and [tag:gnome], personally. I think the [tag:gnome] tag should cover whatever is the latest version number of GNOME (with, say, [tag:gnome2] remaining separate in case users have questions specific to the older version of GNOME pre-11.10 releases use). When GNOME 4 comes along, [tag:gnome] could then cover that and [tag:gnome3] would once again be its own tag, and so on.

I'm hesitant to accept the idea that [tag:gnome-shell] should also be merged into [tag:gnome]. On the one hand, GNOME Shell is intended by the GNOME project to be the official desktop shell for the GNOME desktop environment, so it would make sense that "GNOME" could refer to either. 

However, GNOME also includes more than just the shell, as Unity, GNOME Classic, Pantheon and Cinnamon demonstrate. We could have questions come up which are about the underlying GNOME 3 system itself, and not GNOME Shell or whatever other shell is running on top of it. As such, I think we should recognize that the DE and shell are sufficiently different topics that we keep their tags separate, as well.