This is an interesting essay, valuable for what it shows yet again about the dangers of unfree services. There wasn't any reason to centralize microblogging anymore than there would have been for centralizing blogging, and trying to get everybody in the world to put their blogs in the same place, so that server operator would have all the logs to analyze and sell. Twitter like Facebook is an architectural pathology, and what you're describing is a part of the pathology. Of course, the real point is that by making their data public they are acknowledging that Google already has the opportunity to do so, which means they can't sell it. And Google has the advantage that although they allow everyone else to search the stream, they alone can combine that whole stream with everything else they also have, to create a richer combination than anyone else could make.