On some architectures, shared libraries must be built with -fPIC. On x86 and others, shared libraries may build without -fPIC. This can be wasteful and potentially cause a performance hit.
If you encounter a package that is not building shared libraries with -fPIC, patch the Makefile to build only the shared libraries with -fPIC. More information on PIC is available at the PIC internals wiki page. If you are unsure, please ask in a public developer forum (like the gentoo-dev mailing list or #gentoo-dev irc channel) for help.