System and method for dynamically substituting broadcast material and targeting to specific audiences

An insertion and encoder system monitors broadcasts from a first broadcasting system to determine the presence of segments that can be substituted in a second broadcast. In one embodiment, the system and method determines whether the first segment from the first broadcast had been sold for the second broadcasting system. In this example embodiment, if the first segment had not been sold for the second broadcasting system, it is substituted for a second segment. The system and method accesses an inventory of sold substitution segments and substitutes a sold segment for the unsold segment in real time. In one embodiment, sold advertisement segments are substituted for unsold advertisement segments that are broadcast to a wide audience over the Internet. Segments are selected in accordance with predefined criteria that can include user demographics and/or personal preferences.