I don't think these checkboxes result in spam. I've been receiving spam for ages, since before those options appeared.
These checkboxes are provided as a courtesy to you, not as a spam generator. Did anyone read the link titled "Tell me more about .NET Passport, privacy, and security"? Taken directly from .Net privacy statement:
"You control which .NET Passport participating sites and services receive the information in your .NET Passport profile and .NET Passport wallet. The information stored by .NET Passport is not shared with a .NET Passport participating site or service unless you explicitly choose to provide it by clicking the .NET Passport sign-in link or the .NET Passport express purchase button on that site."
--AND--
"NET Passport will not sell or rent your personal information to third parties."
By checking these options, MSN is sharing your info with .NET partners when you say it's ok, not selling your info to spammers. The following options won't result in more spam. The options are letting you specify what info to share when you click on the .NET Passport sign-in link on the .NET partner pages.
Hence if I check (on the Hotmail site) "Share my e-mail address" and "share my other registration information" and I go to Buy.com and I click the link ".NET Passport sign-in", I will still need to fill in my First and Last names since I didn't check "Share my first and last names".
MSN provided this service so that if you go to a .NET partner and you decided to register on that site (say, for example, buy.com), your info will be pre-filled in. They aren't selling your information to spammers, and they aren't giving your information to these other .NET sites unless you decide to register with those sites. They're just saving you keystrokes by speeding up registration and offering you personalized services. Any e-commerce site (as are most .NET partners) are going to try to offer you content and services- at least if you share your passport info, you'll get content and services which are better tailored to you.
If you go to passport.com, you can see the list of companies whom your info will be shared with. And it's only shared when you decide to register with that site and when you log in to that site. Buy.com won't get my Passport info unless I register with them.
I have 2 hotmail accounts- one which is a spam-magnet and one which is spam-free. The spam-magnet account has been open for > 3 years, the spam-free account has been open for ~6 months.
On the spam-free account, I have checked all of those options for sharing info with other .NET partners and I DO NOT have any junk mail filtering turned on. I've never received a piece of spam. Not one.
On the spam-magnet account, I haven't checked those options to share info with .NET providers, I have Junk Mail Filtering set to High and Immediate Deletion, and I have some other filters set. I receieve at least 10 spam e-mails a day.
I believe that Hotmail addresses were stolen and sold to spammers during the Hotmail server break-ins of 1999. This would explain why my first e-mail address is filled with spam and my second is spam-free. Of course, none of this explains whey Hotmail has such a sucky spam filter, but it's free, so hey.
But I don't believe M$ is directly responsible for the deluge of spam, and I don't believe those checkboxes for sharing info will result in more spam