Snip from NYT story by Miguel Helft:
Google and Viacom said they were hoping to come up with a way to protect the anonymity of the site’s visitors. Viacom also said that the information would be safeguarded by a protective order restricting access to the data to outside lawyers, who will use it solely to press Viacom’s $1 billion copyright suit against Google.Google Told to Turn Over User Data of YouTube [New York Times]
Still, the judge’s order, which was made public late Wednesday, renewed concerns among privacy advocates that Internet companies like Google are collecting unprecedented amounts of private information that could be misused or fall unexpectedly into the hands of third parties.
“These very large databases of transactional information become honey pots for law enforcement or for litigants,” said Chris Hoofnagle, a senior fellow at the Berkeley Center for Law and Technology.
Update: Here's a related statement from the EFF.