Homebrew permission issues

I basically installed Homebrew as described at https://github.com/mxcl/homebrew/wiki/installation.

However, my user account ist not an Administrator account, therefore I substituted my user identity with the one of user admin (su - admin), who is an Administrator. Then, as user admin, I installed Homebrew by executing /usr/bin/ruby -e "$(curl -fsSL https://raw.github.com/gist/323731)". Moreover, I installed giter8 by running brew update && brew install giter8.

Now, as user admin I can run command g8 which is installed in /usr/local/bin. However, using my regular restricted user account, I cannot run this command, as its permissions are too restrictive:

$ ls -la /usr/local/bin/g8
lrwxr-x---  1 admin  admin  29 Sep  2 11:12 /usr/local/bin/g8 -> ../Cellar/giter8/0.2.0/bin/g8

As you can see, g8 has permissions 750 and is owned by admin:admin; so, as regular user, I have no chance to run g8. But, what is even more strange, some crucial folders have similar – too restrictive IMHO – permissions:

drwxr-x---  3 admin  admin   102 Sep  2 11:12 Cellar
drwxr-x---  7 admin  admin   238 Sep  2 11:12 Library

Thus, even after fixing the permissions of symbolic link g8 (readable and executable by all users), regular users cannot execute commands / run programs installed via brew install..., as regular users cannot access folder Cellar, nor folder Library, which both contain crucial files for most programs.

Is this by design, or is this a bug?