I have been following the news about Google OpenSocial for a while.
The idea behind this is to join many Social Networks (and therefor different APIs) in one API. This way you can make web applications that work in all supported social networks.
The list of partners include: Engage.com, Friendster, Hi5, Hyves, Imeem, LinkedIn, MySpace, Ning, Oracle, Orkut, Plaxo, Salesforce.com, Six Apart, Tianji, Viadeo and XING.
Surprisingly enough Facebook is not included as a Partner. Who would of thought? A little tip, read the FAQ. Maybe you will notice Google subtle attack to Facebook! After all Google does not require any special markup languages or plugins. Twice.