The marketplaces feed manager is generally used by e-merchants. The configuration is more or less complex depending on the nature of the feed to be configured and the channels targeted.
It can, however, be used by any actor who needs to transform a stream from one format to another. At Sellermania for example, we use our feed manager, the Mapper, to transform our feed of customer invoices into a debit / credit accounting flow! The Mapper is so flexible that there is almost no limit to the transformation possibilities, and the use goes far beyond marketplace feed management.