Here's the scenario: I configure my browser to host my SharePoint sites in zones that pass through my logon credentials so that I don't have to login when I open a SharePoint site in a browser. I have multiple logins in the domain.
I logon as domain\bill1. I go to the portal and am domain\bill1 to the portal. However, when I go to the portal, I'd rather be domain\bill2, so I use the dropdown on the portal to login as another user and login as domain\bill2.
I click MySite. MySite is another web application that asks for my login credentials and domain\bill1 is passed to the MySite web application. If this is the first time I'm going to MySite, it creates a MySite for domain\bill1. I am not happy. So I go to the dropdown and login again as domain\bill2. Now, I receive the public face of domain\bill1's MySite.
All has functioned in Internet Explorer and SharePoint as expected. My login creditials are not passed from the browser to newly accessed web applications in SharePoint. Instead, those credentials are supplied by the desktop operating system. So, because I initially logged into my desktop as domain\bill1 and then reauthenticated as domain\bill2, the reauthentication was only for that web application. I was still domain\bill1 to the MySite web application and to the rest of the applications running on my desktop.
Just thought I'd point out this little scenario. This will likely product frustrated users and a few help desk calls.
Bill English
Mindsharp