If you have a Hotmail account you already have one. Microsoft just consolidated all of their MSN services together so you can just use one login name and password to access everything. They also want people to save their addresses and credit card information so online shopping sites can use it when a shopper goes to pay for their items. For example ebay lets you log in using a .NET Passport account.
I don't trust storing my credit card info with Microsoft as they always seem to have trouble with security and are always a target for hackers, but otherwise I don't care.
goates