I discovered this thanks to a Freedom of Information Act request I filed with the Department of Justice. The DOJ complied, though rather selectively. I asked for records of government demands for information made to search engines or ISPs from January 2005 to the present.What I got was 54 files related to the Department of Justice's COPA litigation. I find it hard to believe the government hasn't approached search engines and ISPs on a broader range of topics than explicit content. Granted, I didn't ask the Criminal Division of the DOJ. That's mostly because I doubted I'd get anything about criminal cases.
I find it somewhat troubling how the government treats the private sector as its private research arm. I'm sure we've not heard the last of this issue.