Business sites Salesforce.com and Oracle.com have also agreed to adopt the APIs. Google's own Orkut social networking site and customisable home page, iGoogle, are naturally expected to use Opensocial.
Third-party applications will provide a boost to the social networking sector, said David Bradshaw, principal analyst at Ovum. "Users enjoy more functionality, while website owners get more visitors, meaning more advertising revenue," he said.
Application owners can gain revenues in several ways, said Bradshaw, primarily through ads placed in their application.
Facebook pioneered this use of third-party applications on its site, and analysts judged this to be an astute move and an instant success. But the site's insistence on proprietary APIs could prove costly in the long term, said Bradshaw.
Where Facebook asks application builders to jump through proprietary hoops, they might prefer the open APIs associated with Opensocial. "Applications on Facebook will be a lot harder to deploy on other sites and vice-versa, whereas Opensocial widgets should be relatively easy to deploy to between sites," Bradshaw said.
"Opensocial's appeal is straightforward: build for one Opensocial-compliant website and you can deploy in lots of other places too."
The significance, Bradshaw said, is that we are now seeing the first clear challenge to Facebook's appeal. "I think Opensocial has a very good chance [of diverting web traffic]. Facebook may be one of the hottest properties on the web, but it is by no means the only popular social networking website, nor is its continued 'hot' status guaranteed."