The Illinois Supreme Court recently invalidated a "no class action" arbitration clause, holding that the clause was unconscionable (but severable from the rest of the arbitration language). Kinkel v. Cingular Wireless, Inc., ___ N.E.2d ___ (Ill. Oct. 5, 2006). In so holding, the court joined the New Jersey and California Supreme Courts, both of which have reached similar conclusions. The opinion also cites several California Court of Appeal opinions. Consumer Law & Policy Blog has a more detailed summary of the opinion at this link.