Placement of the logout button/link?

In my experience, having a "logout" button/link of some description in the upper right hand corner is (or was) pretty standard. Is this documented/recommended anywhere?

Sites that require javascript have been drifting toward hiding the link in a menu (albeit still a menu in the upper right corner) -- e.g., Stack Overflow, Facebook and Gmail. I've personally found this... violates the "Don't make me think" principle, to put it nicely.

Coincidentally, I just experimented: on SO, you can log in without javascript, but I can't find a way to log out!

So: are there any good documents to reference on this subject?