Amazon has this problem with their "Top 500 Reviewer" category as well. I recently stumbled upon one of these whose reviews were all 5 stars, and all began with the same sentence. A quick look through that list also shows a few Top 500 Reviewers with zero reviews.
"Amazon Bestseller" and "Top 500 Reviewer" are concepts that form a large part of Amazon's brand and value proposition. Regardless of whether this is a bug that can be quickly patched, they should pay more attention to things like this IMHO.