Google Product Search introduced “multi-client accounts” that allow aggregators and marketplaces to consolidate and manage data feeds and reporting for sub-accounts, submit changes more rapidly, and get more accurate Google Checkout badging at the seller level. Marketplaces and aggregators’ll be required to use multi-client accounts to submit and manage their sellers' feeds starting on December 1st, 2009. As a result, individual sellers on marketplaces no longer need to submit a feed to Google Product Search. To avoid duplicate listings, Google’ll notify individual sellers and retiring their accounts.

More info: Marketplace and Aggregator policies