[nrlucas]

Standard not to mention it? Not sure. But it's referenced in other places of the user agreement, see below. Pretty much exactly like the pay-pal opt-out.

Opt-Out Procedure IF YOU ARE A NEW EBAY USER, YOU CAN CHOOSE TO REJECT THIS AGREEMENT TO ARBITRATE ("OPT-OUT") BY MAILING US A WRITTEN OPT-OUT NOTICE ("OPT-OUT NOTICE"). THE OPT-OUT NOTICE MUST BE POSTMARKED NO LATER THAN 30 DAYS AFTER THE DATE YOU ACCEPT THE USER AGREEMENT FOR THE FIRST TIME. YOU MUST MAIL THE OPT-OUT NOTICE TO EBAY INC., ATTN: LITIGATION DEPARTMENT, 173 WEST ELECTION ROAD, DRAPER, UT 84020.

(from, http://pages.ebay.com/help/policies/user-agreement.html)