This seems to be the top news on many message boards and blogs over the past 24 hours. Google's secret lab or "Rater Hub Google" as entitled by Google. It all started by postings on various forums of strange referrals spotted by webmasters in their logs in the form "http://eval.google.com...".

Exactly what this unknown address is about was uncovered when an entry in Search Bristo's blog revealed what goes on behind the scenes. The lab is an area for testers who manually check through Google's search results. I actually don't think it's particularly surprising that Google are doing this. I'm sure most, if not all popular search engines rely on manual testing to some extent, Perhaps their algorithm can "learn" from the users choice to whether a site is spam or not and develop their algorithm as a result.