Is Twitter just for people Twitter members know?

Your Twitter updates are generally read only by the people who "follow" you.
There IS a tab on everyone's home page that says "Everyone", where you can check out the most recent Twits that have been posted across the globe, by anyone and everyone. It gets updated really fast, though, since people are twitting like mad. :)
To my knowledge, there's no way to do a "public address" kind of thing where your Twit would appear in everyone's follow-stream.
It would be too close to spamming, I think... not sure Twitter would allow something like that.

Please, someone correct me if I'm wrong....