See: http://pages.ebay.com/help/policies/user-agreement.html

"You and eBay each agree that any and all disputes or claims that have arisen, or may arise, between you and eBay relating in any way to or arising out of this or previous versions of the User Agreement, your use of or access to eBay's Services, or any products or services sold, offered, or purchased through eBay's Services shall be resolved exclusively through final and binding arbitration, rather than in court. Alternatively, you may assert your claims in small claims court, if your claims qualify and so long as the matter remains in such court and advances only on an individual (non-class, non-representative) basis."

[...]

"Prohibition of Class and Representative Actions and Non-Individualized Relief YOU AND EBAY AGREE THAT EACH OF US MAY BRING CLAIMS AGAINST THE OTHER ONLY ON AN INDIVIDUAL BASIS AND NOT AS A PLAINTIFF OR CLASS MEMBER IN ANY PURPORTED CLASS, OR REPRESENTATIVE OR PRIVATE ATTORNEY GENERAL ACTION OR PROCEEDING. UNLESS BOTH YOU AND EBAY AGREE OTHERWISE, THE ARBITRATOR MAY NOT CONSOLIDATE OR JOIN MORE THAN ONE PERSON'S OR PARTY'S CLAIMS, AND MAY NOT OTHERWISE PRESIDE OVER ANY FORM OF A CONSOLIDATED, REPRESENTATIVE, CLASS, OR PRIVATE ATTORNEY GENERAL ACTION OR PROCEEDING. ALSO, THE ARBITRATOR MAY AWARD RELIEF (INCLUDING MONETARY, INJUNCTIVE, AND DECLARATORY RELIEF) ONLY IN FAVOR OF THE INDIVIDUAL PARTY SEEKING RELIEF AND ONLY TO THE EXTENT NECESSARY TO PROVIDE RELIEF NECESSITATED BY THAT PARTY'S INDIVIDUAL CLAIM(S). ANY RELIEF AWARDED CANNOT AFFECT OTHER USERS."