I disagree with the Users' Mental Models matching. Common users don't use address bar at all, it means nothing for a lot of people. I prefer suggest that more the tabs are close to the surfing zone, better it is. Tabs are more important than the address bar in common surfing sessions. To cite another psychologic law applicable to usability, we can see the [Law of Proximity of the Gestalt laws](http://en.wikipedia.org/wiki/Gestalt_psychology#Pr.C3.A4gnanz "Gestalt in Wikipedia") ;) In the same logic, approach the search bar nearer to the surf zone could also be an element of navigation improvements.

On the other hand, preparing "extra-application" tabs for the future is a good idea, but use it in the title bar is definitely very questionable for the web browser. We can note that Adobe uses tabs for documents in CS4 applications, like we can find it in most of development tools and IDE. This choice is quite good, because switching between documents is a pain in most applications. That said, I could not imagine that we place the tabs in the document title bar, it would be too confusing and would be almost equal to place the documents and the application to a same level, which is false. This mean that the functions in the application are fully oriented for the active document, with no extra action that this particular document can afford according to his nature and his form... could be great in theroy, but complicated and quite confused for the users... I'm stopping here, i'm going to far :) ... So i did never tried to move tabs from a window to another inside CS4 :)

(correct me if my english is too bad ;)