Granted, some limits — such as date restrictions — are easy to apply. But consider the 11th Circuit’s suggestion that “the warrants could have limited the request to messages sent to or from persons suspected at that time of being prostitutes or customers.” How is Facebook supposed to know which messages are from people suspected of being prostitutes or customers? Is the warrant supposed to give Facebook a list of specific suspected prostitutes and customers, such that only messages to and from them (from Facebook accounts known in advance, I gather) can be legally turned over to the government? If so, that seems problematic to me. The point of a warrant is to discover evidence in the place to be searched. I don’t see why relevant evidence involving then-unknown suspects or customers should be off-limits.