The type of information requested in the subpoena; all subscriber information, type of service, payment and billing records, other domain names served by CF associated with the same customer, DNS configuration, and *account access history including any and all authentication, file transfer, web server logs or other transaction logs containing source Internet Protocol addresses related to the subscriber's use of the CloudFlare services.
Cryptome.org raised some good questions about what are CF's policies for retaining access logs to customer sites; http://cryptome.org/2013/04/cloudfare-logs.htm.
>> When Brown went to jail, work on ProjectPM ground to a halt. Even worse, the DoJ now took an interest in everyone else who had participated in ProjectPM. On April 2, the DOJ served the domain hosting service CloudFlare with a subpoena for all records on the ProjectPM website, and in particular asked for the IP addresses of everyone who had accessed and contributed to ProjectPM, claiming it was a criminal enterprise. The message was clear: Anyone else who looks into this matter does so at their grave peril. (https://whyweprotest.net/community/threads/barrett-brown-thr...)
The good news is CF claims they don't retain this data, and there is no legal requirement for them to do so; http://blog.cloudflare.com/what-cloudflare-logs