On the other hand, there is merit to the claim that use of BitTorrent satisfies the requirements of Rule 20(a)(2) for permissive joinder. Rule 20(a)(2) allows a plaintiff to join multiple defendants
in one action if: “(A) any right to relief is asserted against them jointly, severally, or in the alternative with respect to or arising out of the same transaction, occurrence, or series of transactions or
occurrences, and (B) any question of law or fact common to all defendants will arise in the action.”147 Members of a particular BitTorrent swarm can be said to have participated in the “same
transaction” or “occurrence” which will result in at least one “question of law or fact common to all defendants.” If one views a BitTorrent swarm as a “transaction” or “occurrence,” then the IP
addresses comprising that swarm will be part of the “same transaction” or “occurrence.” It can and should be presumed from a plaintiff’s initial complaint that a BitTorrent user affirmatively
chooses to enter a particular swarm in order to make use of other swarm members’ computer resources to download a particular file, while at the same time offering up their own computer’s resources to facilitate the downloads of other members of the swarm. Even though being part of the same swarm does not guarantee interaction between every swarm member,148 plaintiffs should not be required— for purposes of Rule 20(a)(2) at the initial, nascent stage of litigation—to prove that each member of the swarm actually connected and swapped bits of data with each other. Defendants use
BitTorrent not to swap a file with certain, specific others, but to get the file as quickly as possible from whoever may be in the swarm.149 The swarm is essentially the overarching infrastructure that allows the swarm members to connect to one another.150 Therefore, evidence of entering a particular swarm should satisfy the “same transaction” or “occurrence” prong. Additionally, because the question of whether the defendant committed copyright infringement will be a question of law “common to all defendants,” the second prong should be satisfied, since all that is required is that there be any common question of law or fact. Therefore, proof that each defendant entered a particular swarm should satisfy both elements of Rule 20(a)(2) for discovery purposes.