It's old hat to say that Facebook has replaced Blogger and Twitter has replaced Facebook. The latter replacement surely has to do with the prevalence of mobile devices (and the difficulty of "typing" on them), esp. among young people. But what about the former? Both blogs and FB are mostly old farts like me.
If Twitter is also about reduced attention spans, perhaps FB is about reduced patience and time. People post and respond to posts more frequently, because it doesn't take as long - or at least you're not expected to be as smart and eloquent (or prolix). By the same token, one can "keep up with" more people in less time; if Blogger is like a virtual public sphere, FB is a virtual cocktail party (emphasis on "virtual," in both cases).
There are some folks who have done good things with "microblogging" on FB. Ben Friedlander is the first person who comes to mind - pithy posts arising directly from his research and thinking about poetics; the responses tend to be equally good. Sure, it's like overhearing snippets of conversation, but a really good conversation.
The rest of us just make wise-cracks.
In one respect, FB is head-and-shoulders above Blogger: you can SEE the comments to the original post (well, several, anyway). It's like a digest of bulletin boards delivered to your computer. So the dialogic aspect is always in front of your face - unlike Blogger, which seems to think the Comments are the Footnotes. (In Word Press, you can make the comments part of the "main page" of the blog - but the print is so damn tiny!).
A couple items to archive here - I've listened to neither of these, so am saving for later-- Pam Brown talks about collaborating with me and Maged Zaher (the latter became a Tinfish Press ...
1 day ago