A computer implemented process for generating customized, user-specific programming for delivery over a network, each programming unit comprising one or more media items, such as song tracks, and at least one promotional media item, such as a commercial advertisement. The media items are selected in response to implicit user taste data, and promotional media items or ads are selected where a media item associated with the promotional media item matches at least one media data item identified as responsive to the user taste data. The media items and the promotional media items are selected so as to constrain the promotional program unit to incur a net cost of no more that a selected maximum cost, wherein the net cost is determined as a sum of the licensing costs of the selected media items, reduced by a sum of the expected revenues generated by the selected promotional media items.