How to fix Safari 6 on Mountain Lion that doesn't show the full URL in the address bar unless I click it?
I've found that logging out and back in is sufficient for fixing this. Still a pain, but takes slightly less time than restarting (which also recovers from the failure since it forces you as well as all other users to get logged out when the Mac shuts down).
In Safari 8, there is a setting that makes the url visible.
Safari >> Preferences >> Advanced >> Smart Search Field (show full website address)