Dave Winer writes that he can't live without Twitter even though it's a silo:
"I find it's an ideation tool for me. Sometimes just entering a series of connected ideas w/o the ability to go back and edit, forces a certain kind of thinking to come out that might succumb to too much editing."
Dave is an inspiration and part of what I've done here (specifically the Today and date views) arose because of ideas from his blog.
I get what he's saying - by handing over control you've got no option than letting it stand and there's a certain freedom in doing so - but wonder if he's being too literal.
Subscribed to his RSS feed it is readily apparent that he often blogs like a thread of tweets, a paragraph at a time, each appearing as a separate item in your feed reader.
As Dave writes, and constantly tweaks, his own blogging software I imagine it would be fairly simple for him to negate the need for Twitter by constructing an environment where he can't go back and edit his posts once published. At least not without a degree of friction.
(I don't know how his system works.)
Not to put words in his mouth but maybe, because he has absolute control, he feels it would be too easy to return to posts regardless of whatever measures he puts in place.