Here's a great A-B example.
On Twitter, a nothing.
On Facebook, a discussion!
Many of the comments I get on Twitter are really for someone else -- they're responding to the headline of a link I've posted, that I didn't write.
And they're very often not responding to the story, just to the headline. And they respond as if I'm the author. Always leads to misunderstanding. Example.
And 140-characters is a severe limit for people who are good writers, for people who aren't good writers (i.e. most people) it's impossible to understand what they mean.
So you have to ask for clarification, if you have the patience, and the follow-ups are usually just as cryptic.
I think Twitter is a failed experiment. Something about its limits needs to be eased. Or maybe it's time to start over, with a different idea altogether.
A Facebook discussion emanating from a picture of me as a grad student in 1977, programming in the Unix lab at UW-Madison.
The same picture posted on Twitter.