Some permissions got messed up in my KDE install the other day after an update, I'm really not sure how. I tried to fix it by recursively changing ownership of /usr/ to root. Don't do this. This kills the OS. It was technically repairable but like, I don't wanna go through that rigamarole, I just nuked it and restored from a backup.
Sometimes I'm reminded that I often know enough to be dangerous, but not enough to be safe.