It should be locked otherwise you can trick people into clicking on a link thinking it belongs to that company. Google, for instance, does protect against that,

It should be locked otherwise you can trick people into clicking on a link thinking it belongs to that company. Google, for instance, does protect against that, so you can't use http://www.google.com/url?http://www.example.com/ http://www.google.com/url?http://www.example.com/