Yesterday we had a pretty bad bug where bash-completion files were installed into /. Similar bugs occur randomly over time and would be much easier to catch and fix if portage checked the sanity of paths used for installed files. That is, I believe that portage (or the gx86 repo) should have a white-list of locations where packages are allowed to install files and it should bail (with FEATURES=strict) whenever a package installs new files or directories not matching the white-list.