In an interesting article in yesterday’s Sunday Times, Peter Norvig (Google’s director of research) mentioned that a small percentage of Google users are diverted to alternative versions of it’s search engine:

On any given day, Google may be testing a couple of new tweaks of its algorithms – the formulas that decide where web pages appear in the listings. Norvig said the company may divert 0.1% of its traffic through a trial version of its search engine to see if users like the results.

Now 0.1% of its traffic may sound inconsequential, but when you execute over 91m searches per day in the US alone (source: searchenginewatch.com) that amounts to 91,000 searches using modified technology.

This would also account for some of the strange appearances with Google’s SERPs (screenshot of request is there). While the Google Adwords quality feedback system has been known about for some time (click on an AdWords link from Google SERPs, go back to the SERPs and you may see a ‘Was this link useful?’ request), this new system seems to solicit similar user feedback for organic listings. (Here’s a short but interesting side discussion about tainted feedback responses WebMasterWorld.com.)

This is an obvious attempt by Google to weed out the countless spam sites that have plagued their index for quite some time now. Of course, the effectiveness of getting your users to do your work for you must be questioned, and I very much doubt we will see this functionality rolled out to a wider audience (getting prepared to eat hat now that I have said that ).

(You can find some other interesting discussions about Spam over on the Google Webmaster Group.)