Like Atunah mentioned, I use the "Compare books" feature to find reviewers to follow with similar tastes. My favorite method is to find a popular book that I disliked for specific reasons, then go through the bad reviews to find others who gave the same reasons for rating it poorly. I've also done so with books I loved for a given reason. Anyway then I hit Compare books, see what % we have in common, and what they said about my other favorites/least favorites, then decide to follow their reviews.
The highest I've seen thus far is 85%, but I'm sure there's someone out there with even more in common, my book soulmate so to speak.
So GR has a built-in system they could use to lead us to similar reviewers, I just wish they would allow us to just do a search for our closest matches. Like last.fm has with the 'Neighbors' system.