User:Gerv/URL mouseovers in address bar
From MozillaWiki
This is a terrible idea. Imagine a phishing page where most of the page is surrounded by <a href="http://www.paypal.com/">. So the entire URL bar would now be a blue (or whatever) "http://www.paypal.com/" instead of the phisher's URL. Would a user really realise that this was a spoof, and they weren't on PayPal?
The URL bar needs to be a trusted indicator of where you actually are.