Are Intermediaries in the Sales Chain Patent-Liable?
Copyfight 2013-08-28
Summary:

He notes that this suit is not generally unusual - institutions sue over patents fairly often - but has the unusual feature that BU is going after distributors. Typically, one sues manufacturers who are accused of violating patents, and sometimes one sues retailers in order to force a halt to distribution of allegedly infringing products. This suit may be unusual in targeting distributors, who are often middlemen between manufacturers and the actual retailers.
My guess is that BU is targeting these distributors as part of a legal strategy. If the distributors want to be removed from the suit they might choose to do so by going before the judge and explaining that they (no longer) distribute the allegedly infringing product. If the manufacturer can't find distibutors they may be pressured to come to a settlement quickly since the lack of distributors can have the same effect as a court-issued injunction, but much more quickly.