Also, what if for some reason a single machine is shared by two people and they need different versions of some programs installed with Homebrew? Installing everything in /usr/local isn't going to look like a good idea then.
A while ago I floated the idea of having a separate, low-privilege "brew" user that installs things, with the brew command automatically switching to that user, but there was no interest.
Not sure about OS X but common corporate Unix protocol is to make /home/ noexec.
Non-core ( i.e. outside central package management ) installations go to /opt/
Other than this one-liner, which is done once, there really isn't any extra hassle with using the default.
I'd be more interested in why you didn't want to install it there?
"Apple documentation hints that /usr/local will be returned to root:wheel restricted permissions on every OS X update; Homebrew will be adding a brew doctor check to warn you when this happens in the near future."
Aside: I really wish Homebrew didn't encourage having a single user own /usr/local. If they're going to insist on never needing sudo to install things, it should just default to installing in your home directory.
Someone I know puts it in ~/brew and that works just fine, too. His reasoning is that /usr/local/ is for all users, and though he's really the only user on his laptop, it's just wrong to install a bunch of stuff that's just for him into a global user directory.