I was thinking after my previous post and probing the general of the SE sites, we should split the installation into:
install-software: for general software installation instructions. If you are/want build from sources, or the problem is apt/dpkg then you should use the according tags. This will absorb all questions in install-from-source and compiling and only the questions that fit in installation
system-installation: For installations of Ubuntu. Remember that Ubiquity is the graphical installer of Ubuntu and questions about it should use also the ubiquity. This tag should be used for problems with the installation process itself and the use of the installer. Post/pre installations problems, ie. boot, dual-boot, partitioning schemes, have their own tags. The questions that fit from installation, i.e. about installing Ubuntu itself.