/usr/local is the tertiary hierarchy per the FHS, by this naming, there should be no whatever there other than bin/lib/shared/... just like on the primary and s

/usr/local is the tertiary hierarchy per the FHS, by this naming, there should be no whatever there other than bin/lib/shared/... just like on the primary and secondary hierarchies, whereas /opt is the wild wild west, often organised by software package (/opt/android-sdk), even with side by side versions (/opt/ree-2012.02), or by vendor (e.g /opt/oracle/java-7-sdk). This is merely a convention, not set into the 2.3 standard apart from the naming 'tertiary hierarchy' otherwise implying this, but it's nonetheless a widespread enough convention — notably in use by every single configure/make/make install (and more) source distribution out there, whose default PREFIX is /usr/local — that we can expect it to be standard behavior.