Cory Doctorow is Canadian. Though I guess that doesn't mean he's not capable of typical American thinking. And perhaps you meant American as in 'North American'.

There are a lot of reviews on Amazon and other retail sites written by people who clearly do not own the product. A lot of reviews are written by people who don't understand the concept of a review. You can find reviews for things which aren't even available to buy yet but Amazon have created a product page for. Seems to me there's a very easy to get rid of reviews people are being paid to write or are just idiots - sites should only allow people to post reviews for products which they have actually bought from that site. It would be easy enough to implement, just check against the would be reviewer's order history. Sure there would be a lot less reviews, but the ones that do get posted will worth something. Quality, not quantity.