Via CNET Webware, today both Facebook Connect and Google Friend Connect launched. Both are services that let you sign on to third party sites using your credentials from the respective site. While this feels like a trip back to 1999 when Microsoft launched Passport as a single-sign-on service (what was Passport is today Windows Live ID, and it's not open to third parties anymore). Arguably Microsoft's biggest mistake back then was asking thousands of dollars in licensing fees for those wanting to implement it. In 2008, in Web 2.0, you can't charge for anything, so there's no cost associated with either.
Both Facebook and Google's Connect services go beyond what Microsoft was offering back then. Both allow the third party site to access the user's contacts, in the case of Facebook, a user's privacy settings as propagated as well. Facebook Connect lets those sites then publish items back to the user's news feed. Google Friend Connect ties into OpenSocial, allowing third party sites to make use of social widgets. The root functionality of these two services— single sign-on—is the same, but the implementation and other features offered differentiate them a fair bit.
These systems still run into the argument that many used against Microsoft Passport: a single point of failure, controlled by a corporation. OpenID, an open protocol, decentralized single sign-on system, has come to maturity lately, but uptake and use is slow. Many large services such as Google and Yahoo act as OpenID providers, but much fewer sites actually accept OpenID credentials. Google Friend Connect actually accepts OpenID among others, but to an average user who already has a Google and Facebook account, OpenID is just something they don't understand. For many developers, the closed system where most people already have an account is much more appealing.
Eight years after Microsoft tried to solve the single sign-on problem, it's intriguing that it's taken this long for others to try in their footsteps. That's eight years of making separate accounts for every site you use. We have the technology to solve this, but can we settle on agreement of how?