But federal court rulings repeatedly agree that no duty exists to search these out.[76] In particular, in MGM Studios, Inc. v. Grokster, Ltd. the Supreme Court looked at "substantial noninfringing uses"; mere lack of monitoring was not by itself sufficient to show wrongdoing or inducement.[76] It may not be possible (or reasonable to require) the host to know and identify what activity is legitimate or not, as file sharing may be used by many content creators.[77] Deletion after a limited period of non-download is suggested as evidence of a motive.