This obviously breaks locally installed libraries.
IMHO /etc/ld.so.conf shouldn't contain anything by default, it is the responsibility of packages which install libraries in certain directories to make sure they are in ld.so.conf before running ldconfig.
I'm talking about software with libraries in /usr/local which are usually installed from source, not about RPMs. Or do you think any "make install" should modify /etc/ld.so.conf?