Your world file contains every package you have explicitly installed. Dependencies for these files are not added, but checked for when needed instead.
It seems .libs and anything with a version number don't really belong in the world file, and portage can track dependencies infinitely better than I can.
I'm using MCE lite, and I have 1982 lines in world! I"m using Gnome, but world includes kde, xfce, stacks of .libs, ect.ect.
Can someone verify what I can remove?