Google on Friday unveiled a new way to help you connect with your friends: its new social graph API for developers. Programmers using the API can build in features to services that allow a user to quickly add existing friends without a lot of back and forth, reducing one of the biggest barriers to entry for using a new social service.

The Google API can grab data from popular services and companies such as Twitter, Flickr and Six Apart, but it can’t track your Facebook and MySpace pages because they don’t use the programming tags the API tracks. The social graph API crawls the web looking for XFM and FOAF tags on the public Internet to determine who you link to and who links back to you.

Google maintains that this shouldn’t frighten privacy advocates because it only amasses data on the public web and it requires mutual link love to, for example, connect a person’s blog with their Twitter account. So both the person’s blog and their Twitter account have to agree that they belong to Bob Smith. For contacts and friends, it’s a one-way street, but clearly you don’t have to add someone the API thinks is your friend to a service unless you want to. However, if you’re on the Internet, the only way out of the social graph is to take down your pages or living a linkless life. And we all know how hard that can be.

Aside from smoothing the process of joining social services, the social graph API also could help determine how people relate to one another on the web, which evokes tantalizing visions of the semantic web.