"a format for syndicating social activities around the web"

I had no idea this existed. Or maybe I just didn't care when I heard about it the first time. Supported by Facebook, Google, MySpace; not used by LinkedIn.

From the rationale:

And if I haven’t made it clear what I’m talking about, well, we’re starting with an assumption that activities (like the ones in Facebook’s newsfeed and that make up the bulk of FriendFeed’s content) are kind of like the synaptic electrical impulses that make social networking work. Consider that people probably read more Twitter content these days than they do conventional blog posts — if only because, with so much more content out there, we need more smaller bite-sized chunks of information in order to cope.

So starting there, we need to look at what it would take to recreate efficient and compelling interfaces for activity streams like we’re used to on FriendFeed and Facebook, but without the benefit of having ever seen any of the services before.

In other words, how can we make the user the center of gravity again, instead of a bunch of applications that want to own the user.

Exciting!