If I am logged in on StackOverflow, and click "Log out", first of all, it shows some log in IDs info and a few more lines.
Under usual circumstances on most other websites, at this point I should be logged out already. But StackOverflow won't. It will require you to pinpoint yet another button "Log out" and then click it again, so that you are logged out.
AND, you are not really logged out. If you come back to StackOverflow and click Log in, after 2, 3 seconds, it automatically logs you in, without asking for your password.
Maybe the "Log out Globally" can work something better. But I wonder, if I am at Apple store or at a net cafe, how do I know I logged out but really didn't? Somebody can come back to StackOverflow.com and log in automatically and do everything that I am allowed to?