hey there, i enjoy your blog.

a few thoughts on the Passport/Visa thing. one, the big money in credit cards really seems to be on the banking side, merchant bank accounts on one side and consumer accounts on the other. that's why Visa Inc. is just an association of banks (which own and operate and cage it -- check out Joe Nocera's excellent book 'Piece of the Action' for all of the innovative things Visa was trying to do in the late 70s/early 80s that member banks wouldn't allow, like a universal ATM and debit/check card that ran on its network).

theoretically, it would be easier for Microsoft to build a CC network from the ground up these days (for real-world card swipes), since the main thing Visa brings to the table has been a network and database infrastructure for all the steps involved in a transactions, from clearing the purchase to handling inter-bank accounting. that sort of infrastructure is obviously a> more widely deployed among small businesses these days and b> sufficiently close to MSFT's core strengths that the notion it could get merchants to sign up for yet another card network isn't that far fetched (why do they have to dial in to visa when they probably have their own net connections or system for clearing multiple cards?).

but it has yet to be shown that the network portion of the CC biz is high margin (or even profitable). but who knows, maybe they'll buy a bank -- certainly lots of folks were doing it in the early 80s (see nocera again) and it just might be the key not only to a successful online/offline payment standard but also a trustworthy, low cost person-to-person payment network ala payPal.

also, if i am not mistaken the merchant fee (the 3 percent figure) is levied not by Visa Inc but by the particular merchant bank, and i do believe they compete with one another on that. i could be wrong but that's my recollection from reading nocera. if that's the case this is another area where MSFT needs to own a bank for your plan to work.

so what's more likely -- MSFT learns the banking business and gets stores to trust them with a major part of their billing, or the banks that make up Visa and MasterCard and already have financially intimate relationships with thousands of merchants (from Amazon to the Gap to 7-11)learn to put together a sufficiently advanced technical back end to make this happen/ i honestly don't know. but it's not as clear-cut in Microsoft's favor as you seem to be making it out to be.

PS if i recall correctly spolsky says that if and when you do need to rewrite code, you absolutely do not stop development on the old code base until you have shipped the new code.

PPS i'm with the audience on the authentication network question. i'm not technical but the whole idea just reeks of 'buggy!' 'insecure!'.

cheers ryan