Out-Law reports that Google was ordered by Justice Rimer to hand over the information on an advertiser to Helen Grant for copyright infringement. Helen Grant "complained that a Google advert led to a service which she claimed violated her copyright in a forthcoming book."
A search brought up a site named Realityunlocked.com, "which offered a free download of an earlier draft of the book, and that the site violated the Trust’s copyright." Google asked Grant to take the issue to court, this way Google does not have to worry about the privacy issues with handing over the information.
Source: Search Engine Watch