Media are structured according to three economic models : publishing, press, flow. This structure can emphasize some current evolution in the library sector. First, we must admit that it refers to a real sector and not to a simple distribution of cultural industries. Second, the growth of databases would progressively set up a new economical model, combining technology, rates and collection of services. The general evolution of public services, the explosion of cultural industries and the emergence of informational industries led libraries to define again or simply define strategies. Taking into account that the imaginary of a collectivity is always political, perhaps one day, it will be possible to propose several economic models of management of collective memory.