Despite significant hurdles, the defendant class action in a patent infringement case is a potentially useful alternative to multiple lawsuits in many jurisdictions because a patentee who emerges from the class action proceeding with a favorable Markman ruling and a declaration of validity should normally be in a very strong position to collect damages. While nothing on the face of Federal Rule of Civil Procedure 23 precludes its application to defendant classes in patent infringement cases, the 23(b) requirements will be a major obstacle in convincing a court to certify a class of alleged infringers. Other practical considerations include personal jurisdiction, venue, due process, collateral estoppel, and substantive patent law. The trick however, given the current state of the case law, will still be getting a class certified in the first place.
Donald E. Burton, The Metes And Bounds Of The Defendant Class Action In Patent Cases, 5 J. Marshall Rev. Intell. Prop. L. 292 (2006)