You do realize the difference between one way and 2 way communication right? In the instance you're referring to, I'm TALKING to someone. A weird concept for you, I know. Actually interacting with another human being and them REPLYING. I'll let you catch up for a minute.
http://twitter.com/uncollege (blatant attempt at getting you to click this)
Now that your head has stopped spinning, let's get back on track. Remember what we were talking about? Posting vs communicating. Right. So. Hold on to your seat because this one is REALLY going to blow your mind. Twitter, yes that thing we've all been talking about, is a great place to broadcast and share with people who follow you. Now, if you don't mind, scroll down a bit. Take a look at some of the things that don't specifically start with @.... See those things? Yea? Click on them. Maybe the air you're wasting won't be completely lost if you can pick up a few things from those posts and articles.
And while you're at it check out
http://twitter.com/uncollege