Open URLs without prefix 'http://' from command line
As @Mark said,


  A URL must begin with a protocol ie the bit before the : so what you have is not a URL.


You'll need to create your own wrapper for the open command. For example, you can use this function to prepend http:

function openweb() { open http://$1 }


Run with openweb google.com or openweb www.google.com.

Place this in a profile file such as ~/.bash_profile to be available in all interactive shells.