Xcode kept asking for license agreement

This may be incredibly specific and boring for most people, but: It turns out that if somehow your /Library/Preferences folder isn't world-readable, Xcode will ask you for license approval every single time you start it (or you run any of the command-line development utilities).

I thought somebody out there besides me, searching the web, might want to know that. I don't know how the permissions of my /Library/Preferences folder changed, but it did somehow.