A content distribution system is provided to facilitate e-commerce transactions for products and services associated with distributed content. A content stream comprising content blocks, reference content blocks and floating reference content blocks uses metadata to identify products and services associated with content blocks. The metadata and floating reference content blocks are used to substitute dynamically selected content for content blocks based on profiles of user(s), the broadcast station, the advertisement spot defined in the stream and content available for substitution. A market server determines optimal matches to support content substitution, and performs brokerage and bidding functions among suppliers of products or services associated with content selected by users.