Recent announcements of Google's authentication service have prompted comparisons to Passport, and even gotten to Dick Hardt (of "Identity 2.0" fame) to call it the, "deepening of the identity silo." I'd like to contrast Google's work with Microsoft's recent work around Live ID.
Microsoft's Live ID *is* the old Passport -- with a few key changes. Kim Cameron's work around the identity metasystem has driven the concept of InfoCards (now called CardSpace) deep inside of Microsoft. In essence, Kim's idea is that there is a "metasystem" which utilizes WS-Trust to translate tokens, so that all identity systems can interact with each other.
Of extreme importance is the fact that Windows Live ID will support WS-Trust, WS-Federation, CardSpace and ADFS (active directory federation server). This means that A) Windows Live ID can interact with other identity metasystem implementations (Open Source versions, for example); B) that your corporate active directory environment can be federated into Windows Live ID; and C) the closed system that was Passport has now effectively been transformed into an open (standards-based) and transparent system that is Live ID.
Contrast all of this with Google's announcement: create Google account, store user information at Google, get authentication from Google -- are we sensing a trend? While Microsoft is now making it easy to interact with other (competing) identity systems, Google is making it nearly impossible. All of which leads one to ask - why?
I honestly believe that Microsoft is ahead of Google on this one for a very simple reason: Passport taught Microsoft some very painful, first-hand lessons. Passport forced Microsoft (over a period of years) to re-examine their fundamental approach to identity. Further, it forced them to figure out how to monetize the idea of identity applications -- and not simply the aggregation of identity itself. Conversely, Google's business is now built on the aggregation of identity data, and they have yet to walk the painful Passport path.
Will the market force Google to learn the same lesson? I don't know. On the other hand, one company is clearly advancing the cause of "identity 2.0", "web 2.0", "Net 2.0" -- call it what you will -- and that company is Microsoft. The other company is deepening the silo and building the walled garden -- and that is *so* late 90s.