I have /opt symlinked to /usr/opt. Since upgrading to Red Hat 6.0, the 'whereis' command seemingly looks in "/opt/../bin" as well as "/usr/bin": kilroy> whereis whereis whereis: /usr/bin/whereis /opt/../bin/whereis /usr/man/man1/whereis.1 If I "PATH=/bin:/usr/bin" I get the same output above, so this isn't anything in my PATH variable.
A "strings /bin/whereis" indicates that whereis looks in /opt/*/bin. The ".." should be ignored.