Что может сломать emerge --depclean ?

Здравствуйте.
man emerge

--depclean (-c)
...
Also note that depclean may break link level dependencies, especially when the --depclean-lib-check option is disabled. Thus, it is recommended to use a tool such as revdeprebuild(1) in order to detect such breakage. ...

Что имеется в виду? Как может что-то поломаться, если

--depclean (-c)
Cleans the system by removing packages that are not associated with explicitly merged packages. Depclean works by creating the full dependency tree from the @world set, then comparing it to installed packages. Packages installed, but not part of the dependency tree, will be uninstalled by depclean.
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 gentoo, portage