Who would turn down the opportunity to work on an iconic retail brand that spent nearly $500 million last year and ranked No. 22 among all U.S. megabrands in 2009? How about Omnicom Group’s DDB Worldwide and TBWA Worldwide; Interpublic Group of Cos.’ Deutsch; and Publicis Groupe’s Leo Burnett Worldwide, all of which are snubbing Sears, Roebuck & Co. The reason is simple: Sears is demanding that participants relinquish ownership of materials and ideas they present during the review — even if they don’t win the business. That demand is so unpalatable that agencies are opting out — and Sears stands to lose out, unless an enterprising agency can convince it to waive the requirement specifically for them.