"Here at Google, we welcome the development of applications that rely on and communicate with Google services. However, many of these services require that users log into their Google Accounts, and authentication by outside applications has been - until now - somewhat cumbersome. To improve this experience, we are pleased to offer alternatives for Google Account authentication."
Why is that important? Let's say you want to export the sites from Google Bookmarks to another web service, or you want to let a site synchronize Google Bookmarks with del.icio.us. To use a system like this you should be logged in your Google Account.
The new Google Account API lets developers automate authentication from software and web applications. The system is secure because you have to authorize the third party site and that site doesn't see your username and password.
{Via Garett Rogers.}
