On slackware and debian /usr/local is used by some programs sometimes though originally /usr/local directory hierarchy was intended to be a place in which things could be put by the system administrator and be left alone by the system's package updates system. If it was in that folder hierarchy, the system's package system for updates was supposed to bypass it. Actually on both slackware and debian the proper prefix for those systems is /usr in order to put info files where they'll be found by info using the infopath variable. Specifically /usr/share/info/ and this was one of the things preventing me from updating existing outdated org-mode documentation until I figured it out.
