However - this means that if you search for an _actual_ url, it _also_ gets displayed in the url bar.
If you have Google as your default search engine, and you click this url: http://www.google.com/search?q=www.apple.com you will see www.apple.com in your address bar.
Isn't this a vector for a spoofing attack? Couldn't someone craft a "search engine" that makes it look like you're on a facebook.com login page, and use it to steal passwords?