Don't be so critical about crazy ideas; people who invent are only successful if they think outside the box and don't carry much concern for the constraints that currently exist in present day systems (like phising, url structures.... forget about that)
Similarly: I'm hoping that you're also someone who's annoyed when Windows hides extensions. Yes, you can figure out how to restore extensions so you always have the extra piece of information--- but can your mother? Can your nephew? These computer users are learning less about files has "conveniences" them with simpler filenames.
I see only one advantage:
* less screenspace used
But some drawbacks:
* The primary way of navigation is not seeable on start of the thought to go somewhere else anymore (note: maybe not the most common way to go somewhere, given the bookmarks on the startpage and people using only google, but still the primary way when you want to go anywhere now and you understand urls)
* Relying on people understanding tabs
* Introduction of a hidden feature and usage of an already used interaction (double-click on tab)
It seems you want to enforce the opening of a tab when you go somewhere, especially since you have no dedicated and always seeable search-field. And your answer to the comment above implies you maybe want to think about a different navigation concept. Which all is fine in some part, opening tabs when going somewhere fits to my usage-pattern.
But i think that this development (as other browser-vendors try to hide the url too) is aimed at a specific class of users (google-only-users + bookmark-only-users + power-users reconfiguring their browser like they want), letting many other (e.g. all struggling users who just discovered the url) behind.
I would like to browse the internet with only a touch screen; maybe integrate the zoom-in touchpad movement with link previews. Anyone?