Google Search Wiki
This collaborative search tool is designed to allow users logged into Google to feedback to Google on the results they see. They have the option to Promote, Remove or Comment on a result. This tool is not new and first appeared in November 2005 (I think) before vanishing again.
It went live most recently on the afternoon of Thursday 20th November 2008 and is still active now. Users logged in to Google can then customise their results to match their needs. Though the changes made by users will only affect the users when logged in, long term Google will probably use the feedback to alter natural search results for users that are not logged in (normal search results). In the past Google has used real people to ensure quality search results pages (Google filtered out many thin affiliate sites using human testing) and Search Wiki gives Google another testing source, the logged in user. As well as a source of free testing, it is not anonymous. A Google account will have credit card details, search history, email and more juicy data that Google can use to assign a user profile. Google could then decide that users located in Europe might like video results displayed in their SERPs, and American users might like more Blog results and so on. This is a great post about Google's Data Empire.
While conspiracy theorists can continue being in awe of the huge amounts of data Google collects, there is one burning question posed by Search Wiki...
Is this the future of personalised search? If so, where does that leave SEO? How do you optimise for a personalised search?