Craig Ball: Custodian-Directed Preservation of iPhone Content: Simple. Scalable. Proportional. Interesting, but not sure I agree - the comments (including mine I hope!) are interesting as well.
My contribution: how is using an iPhone backup for preservation any different from e.g. using a PC or system backup for preservation? And there is significant case law in the US that reflects on that approach through the lenses of cost shifting, accessibility of the underlying information, etc.