While the article is mostly anecdotal, I've seen that kind of thing happen. I even protested one "reviewer"'s one-star review for Attica Locke's wonderful Black Water Rising: A Novel, a rating based solely on the fact that the Kindle edition was initially priced at more than $9.99.
I have mixed feelings toward Amazon. On the plus side, I use it like Books in Print. It's the first place I go if I want to get a snapshot of the book. And I'm making some nice money since I put my old books on the Kindle.
On the flip side, Amazon glossed the truth in its recent fight with Macmillan over ebook prices. They pretended they were fighting for the consumer, when it was really about their bottom line. And I think Amazon wields too much power. I'm glad Steve Jobs is helping bring some balance back into the marketplace.