[rhizome]

I don't think so. I think they're backgrounding (side-bar'ing) random friend activity and designating the center stream for capital-c Content. Subscriptions, active threads, messaging from Like'd entities...the center box is commerce-oriented, the sidebar is for communications and for contributing to entities (comments, photos, statuses, etc.) defined as candidates for the center stream.

I believe that the center stream will be where the half-page forced-Chevrolet ad is going to go, the changes of late all point in this direction. Think: monetization and profit.

[tmcneal]

Along those same lines, I'd bet that the floating section was added to get more eyeballs looking on the right side of the screen where the ads are.

[rhizome]

I'd say that along those lines, one aspect of the purpose of the sections is that the center is long-form attention and the right sidebar is short-form "constant check" attention.

And just to put the button on it: I fully believe that FB is at least this cynical when it comes to the design of the page.