defaults write com.apple.finder PathBarRootAtHome -bool TRUE;killall Finder
The changes will take effect immediately. Should you wish at a later date to revert to the default path bar, open a Terminal window and type the following:
defaults delete com.apple.finder PathBarRootAtHome;killall Finder
source:
http://osxdaily.com/tag/mac-os-x-10-7/page/4/