I would definitely consider it if there is sufficient compensation, although it's hard for me to think of a specific number.  The reality is, though, I would probably modify my browsing to some extent.  Sitting around talking with friends at home sometimes leads to unusual topics of conversation that can lead to searches on weird topics.  I'm not sure that I would to do that with some of our more, er, exotic topics of debate knowing every search was being tracked.  It would seem likely to me that other people would be similar and self-censor themselves to some degree.  Even so, getting paid to do something that you would do anyway does have its appeal, and the majority of the information would probably still have value for Google.