Amazon Dorks

Why do people waste their time writing positive reviews of things on Amazon? Especially if they are not the first review. I mean usually these people say almost the exact same thing as the editorial review or the previous customer reviews. I also don't know why people feel the need to summarize a whole movie, that's not a review.
I have written a couple reviews on Amazon but they were for things I hated, and I felt like I had something original to say in criticism. Maybe I thrive on hate but that's just me.

Oh and why are all these people writing blogs?