What percentage of content on the internet is unique?

I was looking at www.boingboing.net and at the end of each post is a link to technorati showing all the blog comments for that item.
So I clicked on this to see what people were saying about a particular item and found 8 posts that mentioned the item; only ONE of the blog entries actually discussed the item at all, the other 7 "comments" were simply verbatim reproductions of the item.
What is the point of blogs that just reproduce other blogs?, does it take so much effort even to add just a few words to give your view on an item?, if not then why blog?
Also the one blog that didn't just copy the original item only reworded it, no other views / opinions / information was added.