OK so I've tried this on two sites, don't know for other sites..

1 - skype.com

2 - careers.research.microsoft.com

First sign in to one of this sites using your microsoft account and then sign out.. Now open a new tab and open outlook.com or skydrive.com , it will directly open your account.. So what is with signout? Every time we have to open new tab and sign out from outlook or skydrive?