Doc Searls mentions trackback and that it still confuses him. I was in the same boat until I started playing around with it. There has to be a better way to describe it. The easiest I think of is calling it a kind of automated comment that gets posted to a blog post you reference. I think it's a great idea, and agree that someone will find some way to abuse it eventually (though I hope no time soon).
What I wonder is if anyone has started looking at trackback data to see how stories are linked and how quickly some things spread across the net.