without an identity, I don't know how seriously any law enforcement agency is going to take this.
IANAL as usual but it shouldn't take much to subpoena Amazon for hosting/payment details.
http://www.amazon.com/gp/help/customer/display.html/?nodeId=508088How to Serve a Subpoena
If you have a subpoena to serve on Amazon, please note that Amazon does not accept service via e-mail or fax and will not respond to the subpoena. All subpoenas must be properly served on Amazon.com, preferably by mailing the subpoena to Corporation Service Company (CSC), Amazon's national registered agent. Please find below the Washington address for CSC (the CSC office in your jurisdiction may be located through the Secretary of State's website):
Amazon.com, Inc.
Corporation Service Company
300 Deschutes Way SW, Suite 304
Tumwater, WA 98501
Attn: Legal Department - Subpoena
Please note also that providing detailed and accurate information at the outset will facilitate efficient processing of your request. That information will include, for example, e-mail and/or credit card number used to make purchases for retail purchase information; the name, e-mail, and physical address of a seller for seller information; Kindle serial number for Kindle information (please note we do not have GPS location information); and IP address and complete time stamp for AWS information.