What is .net passport and why must I have it?

Hi! Thanks for the question.

The .net passport is a single login service by Microsoft. Basically,
it gives you the power to log-in at Microsoft websites using only one
account. This eliminates the tedious process of creating different
accounts for a variety of services like Hotmail, The Xbox service, and
other Microsoft sites.

Please read the following links to get a better understanding.

?Microsoft Passport Network?
http://en.wikipedia.org/wiki/Microsoft_Passport 

?Passport Network?
https://accountservices.passport.net/ppnetworkhome.srf?vv=330&lc=1033 


You can read some of the benefits of .Net Passport on this page from Microsoft.

?What are the Benefits of .NET??
http://www.microsoft.com/net/basics_faq.mspx#E3C


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Benefits .net passport

I hope these links would help you in your research. Before rating this
answer, please ask for a clarification if you have a question or if
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Regards,                              
Easterangel-ga                              
Google Answers Researcher