Does OS X place any of its own files in /usr/local?
A lot of other apps do put stuff there though (when I wish they'd keep it in their own bundle).
Even worse, a lot of other apps drop stuff into /usr/bin.
You can't even do it with root:
[mason@IT-PC-MACPRO ~]$ sudo bash
Password:
[root@IT-PC-MACPRO ~]# touch /usr/bin/nope
touch: /usr/bin/nope: Operation not permitted
[root@IT-PC-MACPRO ~]# cat 'nope nope' >> /usr/bin/nope
bash: /usr/bin/nope: Operation not permitted