[LiberatedLlama]

Running untrusted software on these sort of systems is fundamentally broken, no matter what the package manager chooses chown or not chown. A malicious program could edit ~/.bashrc to modify the user's PATH, or wrap sudo with a keylogger then use that password to chown anything it likes. That's not even a theoretical but unlikely sort of attack; it's quite trivial.

    > alias sudo='echo not what I expected'
    > sudo foo
    not what I expected

[sirn]

That's fair, but it's only affecting single user, while writable /usr/local affects all users. However most Mac users are single user, so the tradeoff makes sense in this context.