Comment 13 for bug 390724

Because this seems to be going to and fro, let me just state a small fact and put this into perspective:

Right now the most important toolbar button (the one used most often) in Nautilus is also the smallest.
I mean not only is it not the same size as the rest, it is actually smaller!
For whatever reason that might be(GNOME HIG, consistency with other GTK apps etc)

Think about that for a second :D

Since you correctly point out that the scope of the problem is much bigger (GNOME HIG, GTK), I doubt it will be fixed now but lets not pretend it is ideal. It is quite simply and objectively, bad design.