evildictator, this is a paste from the link you provided:
"Additionally, with your permission, we may contact you via phone or email to provide you with promotional offers regarding Microsoft Online Services. You may change your contact preferences in the account management portal."
So, buried somewhere in the portal, is some option that I have to find that says stop harassing me.
And with every change I make I'm sure I'm "opting in" to more harassment.
I don't want to have to trust them. They don't need my phone number. They have my bank account number for Christ sakes. From there the can get my home address If I was a criminal I would spend twenty bucks and get a monthly throw away phone. My phone number is just another way for them to spam me. It is another piece of information about me that they can sell.