Three separate services, each hosting segments of a file that have to be put back together in some way. Either those three sites will have information on how to rebuild the file (revealing the reason they're hosting it in the first place), or there'll be a 4th party involved that provides the information. It starts looking like an organized conspiracy, if a court ends up looking at it. And that's the answer: The target companies file suit against whatever sites seem to be involved in the conspiracy.

Either that, or it ends up being so obscure that the target company(ies) never notice.