Since pacman 4.2, when running yaourt as root user you get an error message. It was really a horrifying experience for me as I run my system as root user.
The fix involves editing the makepkg configuration:
vi /usr/bin/makepkgFind the line that checks for root and comment it out or modify it. This restores the ability to build packages as root.
Warning: Running as root is not recommended for security reasons, but sometimes it’s necessary in development environments.