http://geekiriki.blogspot.com/2011/10/flume-and-hadoop-on-os-x.html
http://ragrawal.wordpress.com/2012/04/28/installing-hadoop-on-mac-osx-lion/
Most instructions for running Hadoop from Homebrew tell you to edit the configuration files in the Hadoop distribution. I'm not a fan of that. Instead, copy the config directory to your home directory, as follows:
cp -r /usr/local/Cellar/hadoop/1.0.3/libexec/conf ~/hadoop-conf
Then edit the files in that directory.