I think the DOJ FAQ are pretty clear:
5. Who is not required to maintain records?
Individuals or entities are not covered producers if their role with respect to covered materials is limited to photo or film processing; distribution; services that do not involve the hiring, managing, or arranging of the participation of depicted performers; providing telecommunications or Internet services; transmission, storage, retrieval, hosting, formatting, or translation of a communication, without selection or alteration of the content of the communication; or dissemination of a depiction without selection or alteration of its content. See 28 C.F.R. § 75.1(c)(4).
6. How does the rule apply to social networking sites?
Most social networking sites would not be covered by the rule because its definition of ?produces? excludes ?the transmission, storage, retrieval, hosting, formatting, or translation (or any combination thereof) of a communication, without selection or alteration of the communication.? Social networking sites would not then normally need to comply with the rule?s record-keeping requirements, labeling requirements, or be required to maintain information concerning their users, and the rule would therefore have no effect on the operations of the site. However, users of social networking sites who post sexually explicit activity on ?adult? networking sites may well be primary or secondary producers. Therefore, users of social networking sites may be subject to the rule, depending on their conduct.
While none of the services discussed above are "social networking sites", the same principles should apply. For full text, see
28 C.F.R. Part 75 SMALL BUSINESS COMPLIANCE GUIDE, Recordkeeping for Visual Depictions of Actual and Simulated Sexually Explicit Conduct.