I've thought EXTREMELY long and hard about this - also because I run a review driven site. I wrote up a blog post talking about some of the more abstract/theore

I've thought EXTREMELY long and hard about this - also because I run a review driven site. I wrote up a blog post talking about some of the more abstract/theoretical concepts revolving around motivation: http://mysimplemindedworld.wordpress.com/2009/04/16/a-framework-for-understanding-motivations/ http://mysimplemindedworld.wordpress.com/2009/04/16/a-framew... So under my framework I'd say the major motivation is that the people contributing reviews are those that are passionate about the Content/Topic. And the simple reason why they get so many is because 1) ridiculous Amazon volume that somebody already mentioned, and 2) Amazon is the place where you voice CAN have the most impact (if you're one of the top).