I see that using other people's twitter posts has become a bit of an issue after Tom Brevoort noted that he was irked that a Blog@Newsarama post consisted of basically just a collection of C.B. Cebulski Twitter posts.
Regarding Twitter, first off, Twitter is a collection of mini-blog posts. That's really all it is. It's a quicker way of making ultra short blog posts (and replies to other people's posts). I've seen some people try to argue that Twitter is more akin to a casual conversation, to which I say, only in the sense that a blog post is akin to a casual conversation. Twitter is just mini blog posts (or mini message board posts, whatever comparison you want to use). In all three cases, your Twitter posts, your blog posts and your forum posts, you're talking about writings that are your intellectual property, no matter how short in length they might be.
That said, when it comes to citing Twitter posts, if you think of them as blog posts, it really makes it a lot simpler.
To wit, no one cares if you quote a hundred words from a blog post (with a link to the blog post you're quoting, of course), because that's just fair use.
However, if you posted an entire blog post without the blogger's permission, I think we'd all agree that that is not good, right? That's not fair use.
That was Brevoort's complaint in this instance. If you collect a pile of CB Cebulski's Twitter posts on how to break into the comic industry and post them as a piece "How to break into the comic industry," you've basically just posted an entire blog post of Cebulski's.
Now, as to this particular matter, David Pepose apparently asked for Cebulksi's permission before doing the post. If so, then there's no problem. Brevoort has even said that yes, there's no issue if the person gives permission for you to republish their stuff in that manner.
So, really, this seems to be a pretty simple situation to me.
If you quote a public Twitter post that's newsworthy (like Warren Ellis talking about Planetary being finished), then fine.
If you quote a whole pile of someone's Twitter posts without permission (particularly if they are written like Cebulski's, where it's clear that it is all part of one larger piece - "how to break into the comic industry"), then not fine.
If you quote a whole pile of someone's Twitter posts WITH permission, then fine.
I think that's about that.