I'm guessing that MS is using the cookie for a purpose that it was not intended ...

bstar77 on Feb 25, 2012 | parent | context | favorite | on: Daring Fireball: Cookies and Privacy

I'm guessing that MS is using the cookie for a purpose that it was not intended for. That's not to say it's inappropriate, but it's up to them to understand the risks and make sure the app works in both states.