The US Department of Justice wants to access user search queries from Google (and other search engines). Of course, initially only to combat child pornography (how often will this be used as an excuse to dismantle privacy?). Those who think they have to agree with this: afterwards, research on child pornography (and, for example, the search for source material for the research - I mean reports about child pornography, not images or films) will also be suspicious. Because with search engine queries, you have the same problem as with email connections and IP connection data: there are gigantic amounts of data, and the search can only take place automatically, making the probability of hits more than questionable.
Those who have ever watched their spam filter struggle to distinguish spam from ham can roughly imagine how promising any search and qualification algorithms can be that only have these mutilated data from the search queries at their disposal ...