Heres a link to craigslist where google is looking for some participants to test usability for some of their products. Looking at the spreadsheet there are few interesting points like:

be willing to install a small piece of software on your home computer that will log your web browsing & searches

This study requires that we identify your searches using a Gmail account. You can use your existing Gmail account or we can create one for you for the purpose of the study.

I wonder what type of tracking they are looking to do that requires installing a new piece of software, and what capabilities/info it would need that the google toolbar doesnt already give them. Concentrating using my big tin-foil hat Id bet it has to do with some Ajax-search-wikiness, since they are pushing it in places I never thought Id see it, like adwords. My money is on them trying to find ways to quantify user data and separate the wheat from the chaff, but thats just me.

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