So someone came up with the five stages of Twitter acceptance: denial ("that sounds stupid"), presence ("I've got an account now"), dumping (posting links), conversing, and microblogging (publishing useful info and conversing). He followed it up with 9 ways to make Twitter more useful for you, which are more aimed at marketing than at being a real person.
I've been on Twitter since April 2007 (username nadyne). I guess I'm somewhere between (4) and (5). Most of my tweets are about conversations, with forays into offering information. Since I'm not here to market (if you've clicked through those links, you'll see that the title of the blog is Influential Marketing), I'm okay with that.