Although certainly a valiant effort, one unintended result is that it will ignore reviews from people who purchase keys via Humble Bundle or other third-party stores. Perhaps that's a negligible portion of the total, but for some games, it may not be. For example, Humble frequently puts up indie bundles for a few dollars, including games that many people wouldn't necessarily buy individually on Steam (because of, for example, the lack of reviews). But at $10 for two games you want and three you've never heard of, you figure, why not? If you end up liking one of those games, your review won't matter... again making it difficult for hidden gems to get a foothold.